Systems Operation

Usage:

Introduction

Reference: For the Electrical System Schematic, see RENR2130.

Power Train Electronic Control System Block Diagram

The Power Train Electronic Control System performs the shifting of the electric shift transmission. The electronic control module (ECM) responds to the shifting requests of the operator by activating the appropriate clutch solenoid valves which then allow oil to flow to the corresponding transmission clutches. In addition to the shifting function, the ECM also controls the neutral start function, lockup clutch function and the backup alarm function.

Also featured is a STIC controller and electronic torque converter. The machines are equipped with many ECMs sharing information via the CAT data link.

Components Description

For the location of components, see the Parts Manual and the Electrical System Schematic in the machine Service Manual.

Electronic Control Module (ECM)

Electronic Control Module (ECM)
(1) Connector J1. (2) Connector J2.

The ECM makes decisions based on input and memory information, then the corresponding response is made through the outputs. The inputs and outputs of the ECM are joined to the machine harness by two 40 contact connectors.

Inputs

Numerous inputs inform the ECM of the status of the machine conditions. Two types of inputs exist; switch type and sensor type. Switches provide an open, grounded, or +battery signal to the switch inputs of the ECM. Sensors provide a constantly changing signal to the sensor inputs of the ECM. The inputs are listed on the Contact Description Chart.

Outputs

The ECM responds to decisions by sending electrical signals through the various outputs. The outputs either create an action or provide information. The outputs are listed on the Contact Description Chart.

Input/Output

The data link is used to communicate with other electronic control modules on the machine. The data link is bidirectional; which allows the power train ECM to receive and send information. The data link allows the sharing of information with other electronic control modules.

All electronic controls that use the data link are assigned a module identifier (MID). The MID for this power train ECM is the number 081.

Switches

Switches provide an open, ground or +battery signal to the switch type inputs of the ECM. Switches are two state devices; either open or closed.

* When a switch is open, no signal is provided to the corresponding input of the ECM.

* When a switch is closed, either a ground signal or +battery signal is provided to the corresponding input of the ECM.

STIC Controller

STIC Controller
(1) Downshift switch. (2) Upshift switch. (3) Direction switch.

The downshift (1), upshift (2) and direction (3) switches are components of the STIC controller and are switch inputs to the ECM. The switches are not individually serviceable. The three switches are serviced as one unit.

The purpose of the downshift switch is to tell the ECM that the operator wants the transmission to downshift one gear. The downshift switch has two input connections to the ECM; downshift N/C at connector J1 contact 26 and downshift N/O at connector J1 contact 25 of the ECM. When the operator presses the downshift switch, the downshift N/C circuit is open and the downshift N/O circuit is closed to ground. When the switch is not activated, the downshift N/C circuit is closed to ground and the downshift N/O circuit is open.

The purpose of the upshift switch is to tell the ECM that the operator wants the transmission to upshift one gear. The upshift switch has two input connections to the ECM; upshift N/C at connector J1 contact 19 and upshift N/O at connector J1 contact 23 of the ECM. When the operator presses the upshift switch, the upshift N/C circuit is open and the upshift N/O circuit is closed to ground. When the switch is not activated, the upshift N/C circuit is closed to ground and the upshift N/O circuit is open.

NOTE: The ECM requires the correct status of the two upshift and the two downshift inputs to decide when to make each shift.

The ECM does not diagnose faults on the upshift or downshift switch.

The direction switch has three positions: forward, neutral and reverse. The purpose of the direction switch is to tell the ECM which direction the operator wants the transmission in: forward, neutral or reverse. The connections to the ECM are: forward at connector J1 contact 30, neutral at connector J1 contact 13 and reverse at connector J1 contact 14. The selected position is grounded. The unselected positions are open.

NOTE: The ECM diagnoses certain failures in the circuit of the direction switch. If an invalid combination of opens and/or grounds exist, the ECM knows a circuit failure is present. The ECM will shift the transmission to NEUTRAL. This fault is then shown on the VIDS message center display; see the subject Diagnostic Operation.

NOTE: The ECM evaluates the switch a while before displaying a fault.

Key Start Switch

The key start switch is an input of the ECM and connects to connector J1 contact 40. The purpose is to tell the ECM that the operator wants to start the engine (has placed the key start switch in the start position). The ECM then initiates the neutral start function; see the subject Neutral Start in the Additional Features section. During normal machine operation, the start terminal of the key start switch is open. When the key start switch is turned and held in the START position, the start terminal closes to +battery and +battery voltage is present at connector J1 contact 40 of the ECM. The ECM then checks to make sure the direction switch is in NEUTRAL and battery voltage is less than 32 volts. If these starting conditions are satisfied, the ECM sends a +battery signal (connector J1 contact 8) to the start relay and engine cranking begins.

NOTE: After the key start switch is initially turned to the START position, the switch will not return to the START position from the ON position. The switch must first be turned to the OFF position, then it can be turned to the START position.

Steering/Transmission Lock Switch

The steering/transmission lock switch is an input of the ECM. The purpose of the switch is to tell the ECM when the operator has the steering/transmission/lock lever in the locked position. If the transmission is NOT in neutral and the lock lever is placed in the LOCKED position, then the ECM shifts the transmission to neutral. Now, if the lock lever is moved to the UNLOCKED position, the ECM prohibits all shift requests until the operator places the direction switch (of the STIC controller) in the neutral position.

NOTE: Two circuits (N/C and N/O) for the steering/transmission lock switch are used for diagnostic purposes. If the two circuits are ever in the same state (open or grounded), the ECM knows a circuit failure is present. This fault is then shown on the VIDS message center display; see the subject Diagnostic Operation.

Quick-Shift Switch

Quick-shift Switch

The quick-shift switch is an input of the ECM. The purpose of the switch is to tell the ECM that the operator wants the quick-shift function to operate. The ECM then enables the quick-shift function; see the subject Quick-shift in the Additional Features section.

NOTE: The ECM diagnoses certain failures in the circuit of the quich-shift switch. If an invalid combination of opens and/or grounds exist, the ECM knows a circuit failure is present. This fault is then shown on the VIDS message center display; see the subject Diagnostic Operation.

Parking Brake Switch

The parking brake switch is an input of the ECM. The purpose of the switch is to tell the ECM the position of the parking brake knob. See the subject Parking Brake Drive Through in the Additional Features section.

NOTE: Two circuits (N/C and N/O) for the parking brake switch are used for diagnostic purposes. If the two circuits are ever in the same state (open or grounded), the ECM knows a circuit failure is present. This fault is then shown on the VIDS message center display; see the subject Diagnostic Operation.

Parking Brake Pressure Switch

The parking brake pressure switch is an input of the ECM. The purpose of the switch is to tell the ECM when the parking brake is engaged.

NOTE: Two circuits (N/C and N/O) for the parking brake pressure switch are used for diagnostic purposes. If the two circuits are ever in the same state (open or grounded), the ECM knows a circuit failure is present. This fault is then shown on the VIDS message center display; see the subject Diagnostic Operation.

Sensors

Sensors provide information (input) to the ECM about changing conditions, such as speed and position. The sensor signal changes in a proportional manner to reflect the changing condition. The type of sensor signals that the ECM recognizes are:

* Frequency - The sensor produces a signal in which the frequency (Hz) varies as the condition changes.

* Pulse width modulated (PWM) - The sensor produces a signal in which the duty cycle varies as the condition changes. The frequency of this signal is constant.

Frequency Sensors

Frequency sensors produce a signal in which the frequency (Hz) varies as the condition changes.

Transmission Speed Sensor

Transmission Speed Sensor - Input

The transmission speed sensor is an input of the ECM. The purpose of the sensor is to allow the ECM to determine the transmission speed. The ECM uses this information to operate the impeller clutch function, ride control (if equipped) and axle protection; see the subject Electronic Torque Converter in the Additional Features section.

The transmission speed sensor is used to measure transmission output RPM. The speed sensor is a frequency sensor. Frequency sensors produce a signal in which the frequency (Hz) varies as the condition changes. This sensor generates a sine wave signal, from passing gear teeth, which is sent to the ECM. The ECM measures the signal frequency (one pulse per gear tooth) and determines the transmission output speed.

The signal wire (connector contact 1) of the transmission speed sensor connects to connector J2 contact 35 of the ECM. Connector contact 2 of the transmission speed sensor connects to connector J2 contact 24 of the ECM.

Torque Converter Speed Sensor - Input

Torque Converter Speed Sensor

The torque converter speed sensor is an input of the ECM. The purpose of the sensor is to allow the ECM to determine the torque converter output speed. The ECM uses this information to operate the impeller clutch and lockup clutch functions; see the subject Electronic Torque Converter in the Additional Features section.

The torque converter speed sensor is used to measure torque converter speed and direction. The speed sensor is a frequency sensor. A frequency sensor produces a signal in which the frequency (Hz) varies as the condition changes. This sensor generates a repeating pattern, from passing rotor teeth, which is sent to the ECM. The ECM measures the signal frequency (one pulse per rotor tooth) and determines the torque converter speed and direction.

The signal wire (connector contact C) of the torque converter speed sensor connects to connector J2 contact 38 of the ECM. The sensor is supplied operating power (+8V) at connector contact A from the ECM (connector J2 contact 12). The speed sensor return (connector contact B is connected to connector J1 contact 15 of the ECM.

Pulse Width Modulated (PWM) Sensors

Pulse Width Modulated Signal

Typical PWM Sensor Schematic

Pulse width modulated (PWM) sensors produce a digital signal in which the duty cycle varies as the condition changes. The frequency remains constant.

Torque Converter Pedal Position Sensor

The torque converter pedal position sensor is an input of the ECM. The purpose of the sensor is to allow the ECM to determine what position the operator has the torque converter pedal in; from not pressed to fully pressed. The ECM uses this information to determine how much to modulate the impeller clutch; see the subject Electronic Torque Converter in the Additional Features section.

The torque converter pedal position sensor is a PWM type of sensor. This sensor continuously generates a PWM signal, in which the duty cycle varies in proportion to the position of the torque converter pedal. The ECM receives the PWM signal and measures the duty cycle to determine the position of the torque converter pedal. The frequency of this signal is constant.

The signal wire (connector contact C) of the torque converter pedal position sensor connects to connector J2 contact 4 of the ECM. The sensor is supplied operating power (+V) at connector contact A from the machine electrical system. Connector contact B of the sensor is connected to frame ground.

NOTE: The torque converter pedal position sensor is sometimes referred to as the left brake pedal position sensor.

NOTE: Also see the related subject Torque Converter Pedal Position Sensor Calibration.

Transmission Clutch Solenoid Valves

Clutch Solenoid Valve Identification

Transmission Clutch Solenoid Valve

The transmission clutch solenoid valves are outputs of the ECM. The purpose of the solenoid valves is to direct pilot oil to the ends of the control spool. The control spool will shift allowing pressure oil to the corresponding clutches. Based on the operators request from the STIC controller, the ECM activates the appropriate transmission clutch solenoid valves.

A transmission clutch solenoid valve is energized by a PWM signal sent by the ECM. Clutch solenoid valves 1 and 2 are for direction. Clutch solenoid valves 3, 4 and 5 are for speed. For movement of the machine two clutch solenoid valves are activated; one for direction and one for speed. When the transmission is in neutral, only clutch solenoid valve 3 is activated.

The clutch solenoid valves have a connector with two contacts. One contact receives power from the corresponding connector, clutch 1 J1-17, clutch 2 J1-11, clutch 3 J2-7, clutch 4 J2-1 and clutch 5 J2-8 of the ECM. The other contact of all solenoid valves join together and return to connector J1 contact 7 or connector J2 contact 3 of the ECM.

With the clutch solenoid valves a pulse and hold strategy is used to extend the life of the coil of the solenoid valves. The ECM has the capability of controlling the amount of current from the output. For ON/OFF type solenoids, the current needed to get a solenoid to engage is much higher than the current needed to keep the solenoid engaged. The pulse and hold strategy makes use of this characteristic of a solenoid by setting the current to the solenoid to maximum and then reducing the current to a lower level after one second. Lowering the current to the valve reduces the heat that is dissipated by the coil of the solenoid.

NOTE: The solenoid coils are not designed for direct 24 DCV operation. The ECM sends a 24 volt PWM signal at a duty cycle which provides an average voltage of about 8 to 12 volts to the solenoid coils. Do NOT activate the coils with 24 DCV (+battery) or the life of the coils will be drastically reduced. If the coils must be activated by means other than the ECM, use a 12 DCV source.

NOTE: Engagement of the neutral clutch is delayed two seconds from the time the operator selects neutral. During this delay, the transmission is in a "no clutch neutral" state, with none of the transmission clutch solenoid valves energized. This "no clutch neutral" state is provided in order to improve the quality of directional shifts. The ECM momentarily prevents the engagement of the neutral clutch as the operator changes from forward to reverse (or reverse to forward) direction.

Torque Converter Solenoid Valves

Impeller Clutch And Lockup Clutch Solenoid Valves (Lockup Clutch Solenoid Valve Is Shown)

The impeller clutch solenoid valve is an output of the ECM and functions as a reducing valve. The purpose of the solenoid valve is to modulate the hydraulic pressure of the impeller clutch. When the ECM increases the current to the solenoid valve, hydraulic pressure at the impeller clutch is reduced; when the current is zero, the impeller clutch pressure is maximum. The ECM varies the current (PWM signal) to the solenoid valve and the solenoid valve modulates the impeller clutch pressure.

The lockup clutch solenoid valve is an output of the ECM and functions as a proportional valve. The purpose of the solenoid valve is to activate or deactivate the lockup function (direct drive). When the ECM sends a high current (high duty cycle) signal to the solenoid valve, the lockup function is activated. With a high current there will also be a high pressure to the lockup clutch when activated. When the ECM does not send a current signal to the solenoid valve, the lockup function is deactivated.

The lockup and impeller clutch solenoid valves are part of a valve body located on the torque converter. The solenoid valves have a connector with two contacts. Connector contact 1 of the solenoid valve receives power from the ECM. Connector J2 contact 13 provides power to the lockup clutch solenoid valve. Connector J2 contact 19 provides power to the impeller clutch solenoid valve. Connector contact 2 of all solenoid valves join together and return to connector J1 contact 7 or connector J2 contact 3 of the ECM.

NOTE: The solenoid coils are not designed for direct 24 DCV operation. The ECM sends a 24 volt PWM signal at a duty cycle which provides an average voltage of about 12 volts to the solenoid coils. Do NOT activate the coils with 24 DCV (+battery) or the life of the coils will be drastically reduced. If the coils must be activated by means other than the ECM, use a 12 DCV source.

NOTE: The lockup and impeller clutch solenoid valves are very different mechanically, although they appear the same. The two solenoid valves must not be switched mechanically or electrically.

Start Relay

The start relay is an output of the ECM. The purpose of the start relay is to turn on and off the start solenoid which controls the starting motor. The ECM then checks to make sure the direction switch is in NEUTRAL and battery voltage is less than 32 volts. If these starting conditions are satisfied, the ECM sends a +battery signal (connector J1 contact 8) to the start relay and engine cranking begins. See the subject Neutral Start in the Additional Features section.

The start relay has a connector with two contacts. One contact receives power from connector J1 contact 8 of the ECM. The other contact (along with the other ECM outputs) returns to connector J1 contact 7 or connector J2 contact 3 of the ECM.

Terminal 3 of the start relay connects to a +battery source. Terminal 4 connects to the start solenoid.

Backup Alarm

The backup alarm is an output of the ECM. The purpose of the backup alarm is to make nearby personnel aware that the machine is backing up. When the operator selects REVERSE, the ECM activates the backup alarm. When activated the backup alarm receives +battery from the ECM.

The backup alarm has two terminals for electrical connections. One terminal receives power from connector J2 contact 37 of the ECM. The other contact (along with the other ECM outputs) returns to connector J1 contact 7 or connector J2 contact 3 of the ECM.

Data Link

The data link is an input and an output of the ECM; at connector J1 contacts 3 and 9 of the ECM connector. The purpose of the data link is to communicate with other electronic control modules on the machine. The data link is not a visible component; it consists of internal ECM circuits and the connecting harness wiring. The data link is bidirectional which allows the ECM to receive and send information.

The information received from other ECM:

Engine speed - sent from engine ECM.

Torque converter temperature - sent from VIDS I/M #1.

Attachment code - sent from VIDS main module.

Service brake pedal switch - sent from engine ECM.

This information is transmitted by the power train ECM to other ECM's:

Transmission gear - sent to VIDS main module.

Steering/transmission lock status - sent to VIDS main module.

Parking brake status - sent to VIDS main module.

Key start switch status - sent to implement ECM.

Transmission requested engine speed limit - sent to engine ECM.

The following information is transmitted by the power train ECM to the VIDS main module:

Torque converter speed.

Transmission speed.

Parking brake switch status.

Start relay status.

Key start switch status.

Torque converter pedal position.

Left brake pedal calibration status.

Left pedal HI calibration valve (torque converter pedal).

Left pedal LO calibration valve (torque converter pedal).

Caterpillar Electronic Technician (ET) also communicates with the ECM's over the data link. After communication has been established, ET will list the ECM's on the machine and the diagnostic information that is available.

All electronic ECMs that use the data link have a module identifier (MID). The MID for the power train ECM is the number 081.

Normal Operation

The primary duty of the ECM is to electronically control the shifting of the transmission. Simply stated, the ECM activates the appropriate clutch solenoid valves to engage the transmission gear that is requested by the STIC controller. The basic components and corresponding requirements for shifting are listed below. (also see Exceptions):

* Attachment Code - The shifting strategy is different on the various machine models. The ECM must know what model it is installed on, so that it operates correctly. VIDS sends attachment code information to the ECM on the data link. From the attachment code, the ECM determines the characteristics of the machine model it is installed on. Attachment code also lets the ECM know which attachments, if any are on the machine.

* STIC Controller - The direction, upshift and downshift switches, located in the STIC controller, tell the ECM the requests of the operator; forward, reverse, neutral, upshift or downshift. The ECM acts upon the shift requests by activating the appropriate transmission clutch solenoid valves. Except for certain conditions, the ECM shifts the transmission as requested by these switches; also see the subject Exceptions.

* Transmission Clutch Solenoid Valves - These clutch solenoid valves, located on the transmission, direct pilot oil to the ends of the control spool. The control spool will shift allowing pressure oil to the corresponding clutches. The ECM decides which clutch solenoid valves to activate, based on the input from the direction, upshift and downshift switches (STIC controller). Clutch solenoid valves 1 and 2 are for direction. Clutch solenoid valves 3, 4, and 5 are for speed. For movement of the machine two clutch solenoid valves are activated; one for direction and one for speed. When in neutral, only clutch solenoid valve 3 is activated.

Exceptions

These are the exceptions to normal shifting as previously described in the Normal Operation section.

* If the upshift and downshift switches of the STIC controller are pressed at the same time, then the ECM does not shift the transmission.

* If the transmission/steering lock lever is placed in the LOCKED position (lock switch activated) when the transmission is NOT in neutral, then the ECM shifts the transmission to neutral. The ECM does not allow other shifts until the transmission/steering lock lever is placed in the UNLOCKED position (lock switch deactivated) and the STIC controller is placed in the NEUTRAL position.

* If the parking brake knob is in the ON (knob out) position (parking brake switch activated) when the transmission is in neutral, the ECM does not shift into first forward or first reverse.

* If the parking brake knob is placed in the ON (knob out) position (parking brake switch activated) when the transmission is in first forward or first reverse, then the ECM shifts the transmission into neutral. When the parking brake knob is moved to the OFF position, the ECM does not allow other shifts until the STIC controller is placed in the NEUTRAL position.

Additional Features

These are the features that are in addition to normal shifting as previously described in the Normal Operation section.

No Clutch Neutral

The no clutch neutral feature is provided in order to improve the quality of directional shifts. This feature momentarily prevents the engagement of the neutral clutch as the operator changes from forward to reverse (or reverse to forward) direction. The ECM delays engagement of the neutral clutch for two seconds from the time the operator shifts into or through neutral. During this delay, none of the transmission clutch solenoid valves are energized.

Quick-Shift

The quick-shift feature is intended to help an operator with a loading cycle that has a high percentage of second gear operation. The operator turns this feature on and off with the quick-shift switch.

With the quick-shift switch activated and the transmission in first forward, the ECM shifts the transmission to second reverse when the direction switch is moved to reverse from forward. When the direction switch is moved back to forward, the ECM shifts the transmission from second reverse to second forward. The operator must then downshift to first forward and the quick-shift cycle can be repeated.

NOTE: The quick-shift feature only functions when the transmission is in first forward and the quick-shift switch is ON.

Neutral Start

The neutral start feature requires the STIC controller direction switch to be in the NEUTRAL position before the engine will crank. The operator controls this feature by placing the direction switch in the neutral position and turning the key start switch to the START position. The purpose of this feature is to allow engine starting only when the transmission is in neutral. When this feature is in operation, the ECM activates the start relay allowing the starting motor to turn.

NOTE: Battery voltage must be less than 32 volts to start.

Backup Alarm

The backup alarm feature is enabled when the operator places the direction switch in the reverse position. The purpose of this feature is to alert personnel that the machine is backing up. When this feature is operating, the ECM activates the backup alarm.

Gear Indicator

The active gear and direction of the transmission is visible on the instrument panel. "F" indicates FORWARD. "N" indicates NEUTRAL. "R" indicates REVERSE. The ECM sends this information to VIDS on the CAT data link.

Parking Brake Drive Through

In the case of a hydraulic failure where pressure oil to release the parking brake is not available, a drive through mode is provided. If the hydraulic failure occurs, the parking brake knob pops out and will not stay in the OFF (knob in) position. To move the machine under these conditions:

1. Shift to neutral.

2. Press and hold the parking brake knob in the OFF (knob in) position.

3. Select FIRST speed forward or FIRST speed reverse.

4. Increase engine speed and the machine will drive through the engaged parking brake.

During this time, VIDS activates a warning category three.

Electronic Torque Converter

The electronic torque converter feature consists of the lockup clutch function and the impeller clutch function. The two functions operate independently.

Lockup Clutch Function

The lockup clutch function electrically controls direct drive. When the ECM activates the lockup solenoid valve, the lockup clutch within the torque converter mechanically connects the torque converter input shaft to the torque converter output shaft. The purpose of this function is to efficiently connect the power train to the engine. The ECM engages the lockup clutch when all of the following conditions are present:

* Torque converter speed is greater than 1400 RPM.

* The machine has been in the present speed and direction (not 1 Forward) for at least two seconds.

* The torque converter pedal is fully released.

* At least four seconds have passed since the lockup clutch solenoid valve was deactivated.

The ECM disengages the lockup clutch when any one of the following conditions is present:

* A shift is made in 1 Forward.

* Torque converter speed decreases to less than 1200 RPM.

* The torque converter pedal is depressed.

NOTE: To prevent engine overspeed, the lockup clutch can not be engaged when torque converter speed is greater than 2250 RPM.

NOTE: During engagement of the lockup clutch, impeller clutch pressure is maintained at system pressure 2275 ± 207 kPa (330 ± 30 psi).

Impeller Clutch Function

Torque Converter Pedal - The position of the torque converter pedal is used to determine the impeller clutch pressure. Depressing the torque converter pedal reduces the impeller clutch pressure, which makes more engine power available (for steering systems) and also reduces maximum rimpull (allows the operator to control wheel slippage). Fully depressing the torque converter pedal engages the service brakes.

Directional Shifts - When the operator requests a directional shift, the ECM:

1. Ignores the torque converter pedal position, if a pressure that is higher than the hold pressure is requested.

2. When the shift begins, the impeller clutch pressure is reduced and maintained at a hold value of 550 ± 207 kPa (80 ± 30 psi).

3. When the ECM determines that the transmission clutches have engaged the impeller clutch pressure is increased to a maximum value, about 2584 ± 207 kPa (375 ± 30 psi). This maximum impeller clutch pressure is maintained for one second, then reduced to about 2274 ± 207 kPa (330 ± 30 psi). This pressure is known as the top pressure.

4. The impeller clutch pressure is increased to maximum pressure to ensure that the impeller clutch engages quickly, but once it has engaged, impeller clutch pressure is reduced to extend impeller clutch seal life. The top value is maintained until conditions (torque converter pedal position, engine speed, lockup clutch engaged) require a change of impeller clutch pressure.

Engine Response Function

To increase engine and machine response during engine acceleration from low idle, the impeller clutch operates as follows:

* The position of the torque converter pedal is ignored, unless a pressure less than the engine response function is requested. (Braking is not affected.)

* During the progression from low idle to 1100 RPM, the impeller clutch pressure is maintained at a hold value of 551 ± 207 kPa (80 ± 30 psi).

* During the progression from 1100 to 1300 RPM, the impeller clutch pressure is gradually increased to the maximum value. The top value is maintained until conditions (torque converter pedal position, engine speed, rimpull control) require a change of impeller clutch pressure.

Reverse Turbine Function

Damage to the torque converter can be produced when the machine is allowed to move backward while on an incline and a forward gear is engaged and impeller clutch pressure is low. The reverse turbine function reduces the temperatures that are created when the machine is operated in this manner. If the torque converter speed is greater than 500 RPM in a reverse direction, the ECM increases the impeller clutch pressure and the torque converter pedal is ignored. (Braking is not affected.)

Engine Speed Controlled By The Power Train ECM

At times, engine speed is determined by the power train ECM. The power train ECM regulates engine speed to provide axle protection and controlled throttle shifting. The power train ECM sends a transmission requested engine speed limit to the engine ECM by means of the CAT data link. Once the engine ECM receives the transmission requested engine speed limit, this speed is compared to the other engine speed inputs, like the throttle pedal. The engine ECM compares these speeds and selects the lowest one to use as the desired engine speed. The engine ECM then controls the fuel delivery to the engine to try to achieve the desired engine speed.

ET is especially useful in troubleshooting problems with these features. With ET, the parameters used by the ECM's to perform these features can be viewed and problems quickly identified.

Axle Protection

The purpose of this feature is to control the torque delivered through the power train while dozing to balance the machine's capabilities with the performance requirements. By controlling engine speed, the power train ECM is able to manage the loads on the power train. Managing the power train loads extends the power train life while maintaining dozing performance.

The power train ECM provides the axle protection function using information from the power train ECM, the engine ECM, and VIDS Interface Module #1. The power train ECM uses the CAT dat link to get the information from the other ECM's.

Axle protection is automatically initiated when the power train ECM determines that the machine is in 1 Forward. Once enabled, the power train ECM sends a transmission requested engine speed limit to the engine ECM to control engine speed.

Enabling Axle Protection

The power train ECM determines that the machine is dozing and enables axle protection when the following condition exist:

* Transmission in 1 Forward.

When axle protection is activated, the power train ECM sends a transmission requested engine speed limit to the engine ECM by means of the CAT data link. The transmission requested engine speed limit will vary between 1585 and 2500 rpm. The actual value varies based on engine speed, torque converter speed and torque converter pedal position.

Disabling Axle Protection

Once axle protection is enabled, the following condition will disable axle protection:

* Transmission not in 1 Forward.

When axle protection is not activated, the power train ECM sends a transmission requested engine speed limit of 2500 rpm, effectively disabling the strategy.

NOTE: The engine ECM's high idle setting of 1865 rpm will prevent the engine from exceeding 1865 rpm.

Converter Stall Speed

Two different engine stall speeds can be measured during a torque converter stall check. One stall speed will be measured when axle protection is active and another when it is not active.

Impeller Clutch Interaction

When the converter output torque is being reduced by the impeller clutch, axle protection may not need to regulate engine speed. The axle protection strategy determines if it needs to regulate engine speed by monitoring the torque converter pedal position.

Axle Protection When Faults Are Detected

Axle protection requires information from machine sensors and a functioning data link to operate properly. When the information required by the power train ECM for axle protection is not available, then the ECM operates in a failure mode. Failure modes of operation are described below.

Failure Mode - Fault With Transmission Speed

This failure mode is used when any of the following faults are active.

A fault of the following prevents the power train ECM from determining if the machine is dozing.

* Transmission output speed sensor.

When faults are active, the power train ECM assumes that the condition based on the missing sensor information is in the state that enables axle protection.

Failure Mode - Fault With Torque Converter Speed or Data Link

This failure mode is used when any of the following faults are active.

A fault with any of the following prevents the power train ECM from calculating the proper requested engine speed.

* Engine speed sensor.

* Torque converter speed sensor.

* Loss of data link communication between the power train ECM and engine ECM.

When any of these faults are active and axle protection is enabled, the power train ECM limits the maximum transmission requested engine speed. The maximum limit on the requested engine speed depends on the specific fault (see above chart). The ECM continues to calculate the requested engine speed using the functioning sensor information. The resulting transmission requested engine speed may be lower than the values listed in the above chart.

The following examples are given to illustrate this failure mode. For these examples it is assumed that the conditions required to enable axle protection are already met and axle protection is enabled.

Example 1 - If the power train ECM looses communication with the engine ECM, then the power train ECM will request an engine speed of 1593 rpm.

NOTE: It is likely that if the power train ECM can't communicate with the engine ECM, then the engine ECM will never receive this request. Consequently, the engine ECM has a similar failure mode. If the engine ECM looses communication with the power train ECM for 5 minutes, then the engine ECM will derate the engine.

Controlled Throttle Shifting (A Failure Mode)

Enabled during a direction shift when any of the following faults are active.

Controlled throttle shifting is only activated when an electrical fault is detected on the torque converter impeller clutch solenoid valve circuit. Once activated, the power train ECM sends a transmission requested engine speed limit to the engine ECM to control engine speed during transmission directional shifts. The purpose of this feature is to reduce the energy absorbed by the directional clutches during a direction shift. This allows the machine to be operated without the impeller clutch until a repair can be made.

The power train ECM is constantly checking the impeller clutch solenoid circuit for faults. If a fault is detected, the ECM will record a fault in the circuit.

When a direction shift is requested and a fault is active, the power train ECM sends a transmission requested engine speed limit of 1400 rpm to the engine ECM by means of the CAT data link. The power train ECM will hold this engine speed request for 1.0 seconds if shifting into forward, and 1.4 seconds if shifting into reverse.

Direction shifts made at engine speeds below 1400 rpm are not affected by this strategy.

Attachment Codes

The attachment code is a code that is entered into the monitoring system and is stored on the VIDS Main Module. The attachment code is an input of the VIDS Main Module and is used to identify what attachments a machine is equipped with. The attachment code tells the power train and engine ECMs' what they can do within the physical limits of the machine. If the attachment code does not match the actual attachments on the machine, a service code may be generated on the monitoring system.

The attachment code can be viewed through the MSTAT program code by entering "MSTAT" and then pressing "OK" on the keypad. The ">" key must be pressed until ATTACHMENT CODE is displayed on the monitoring system.

If the attachment code is not correct, the service program allows the operator to configure the attachment code for the machine by entering "ATTACH" and then pressing "OK" on the keypad. The desired attachment code can then be entered from the keypad by entering the desired attachment code followed by "OK".

When a valid attachment code has been entered, the system will ask you to enter the code again. If the same code is entered again, this code will be accepted as the new attachment code. If the same code is not entered at the second prompt as was at the first prompt, the code will not be accepted. If an invalid code is entered at either prompt, or if the "OK" key was entered at either prompt (before entering a number) a new attachment code will not be accepted, allowing the old attachment code to remain valid.

NOTE: The following chart lists the correct attachment codes for the 854G Wheel Tractor.

Diagnostic Operation

The ECM detects faults that occur in most of the input and output circuits. A fault is detected when the signal (at the contact of the ECM) is outside a valid range. The ECM then records the fault. If the fault goes away (not present), the fault information remains stored for 150 hours in the ECM and until cleared in VIDS.

The diagnostics of the ECM are available to assist with the troubleshooting of detected faults. A service code is used to specify each detected fault. The service code consists of three identifiers (MID, CID and FMI). The service code is shown in the message area of VIDS. Faults can also be viewed with ET. The identifiers are:

* Module Identifier (MID) - The MID is a three digit code shown on the display area. The MID is displayed with the service code. The MID tells which ECM diagnosed the fault. Some MID's are:

Engine ECM ... 036

VIDS Main Module ... 049

VIDS I/M #1 ... 057

Power Train ECM ... 081

NOTE: The MID of the power train ECM is 081. When troubleshooting the power train system, make sure the number 081 appears with the service code of the fault. VIDS also shows service codes of faults that are not related to the power train system. The MID number 081 identifies the service code as coming from the power train ECM.

* Component Identifier (CID) - The CID tells which component or circuit is faulty. For example; start relay or reverse solenoid. The CID is a three digit code shown on the display area. The MID, CID and FMI are displayed together.

* Failure Mode Identifier (FMI) - The FMI tells what type of failure has occurred. For example; voltage above normal, current below normal or abnormal frequency. The FMI is a two digit code shown on the display area. The MID, CID and FMI are displayed together.

NOTE: For a list of CID and FMI codes for the power train ECM, see the Service Codes chart under the topic Troubleshooting Faults With Service Codes in the Testing And Adjusting section.

The power train ECM does not have a display area for showing diagnostic information to service personnel. Diagnostic information concerning the power train system is sent on the CAT data link to VIDS. Service personnel must be familiar with VIDS in order to troubleshoot the power train system.

EACK and ELIST of VIDS allows service personnel to see and to troubleshoot the faults that the power train ECM has detected. While VIDS is in EACK or ELIST, the fault or service code for any detected fault of the power train ECM is shown in the display area of VIDS.

For more information, see "Troubleshooting System Events" in the Testing And Adjusting portion of this manual to troubleshoot the faults for the power train ECM.

VIDS Normal Operation

Gauge Cluster Module
(1) Gauge warning area. (2) Pictograph symbol.

Speedometer/Tachometer Module
(3) Tachometer. (4) Pictograph symbol. (5) Ground speed readout. (6) Transmission actual gear readout.

Message Center Module
(9) Alert indicator. (10) Data logging indicator. (11) Message area. (12) Universal gauge. (13) Gauge warning area.

This section contains a brief overview of the VIDS system. The purpose of this section is to provide the information required to:

* Get diagnostic fault codes.

* Run service procedures.

* Clear fault codes.

* Enter attachment codes and verify.

NOTE: For a full description of the VIDS system see Service Manual SENR1371.

During normal operation, the VIDS display components show the operator and service person:

* Whether VIDS is operating properly. Whenever the key start switch is turned to the ON position, some VIDS outputs (gauges and message center module) briefly operate. VIDS is performing a test. For a complete test of the VIDS outputs, see the topic Self Test.

* A value for system condition. VIDS continuously watches machine systems. The gauges in the gauge cluster module show a normal range value (in the central region).

* Whether a machine abnormal system condition (machine event) exists. VIDS continuously watches machine systems. When an abnormal condition (problem) exists, alert indicator (9) FLASHES and message area (11) shows what system parameter has an abnormal condition and what the condition is. Universal gauge (12) also shows the approximate value of the abnormal parameter. The event is stored in the main module memory. As the severity of the problem increases the action lamp FLASHES and the action alarm SOUNDS. See Warning Operation section.

* Whether an electrical system fault exists, VIDS continuously checks for electrical faults in VIDS and other electronic control module systems (engine, power train, etc.) on the machine. When a system fault is detected, the fault is shown on the message area and stored in the main module memory. See Service Operations section.

VIDS enters normal mode when it is powered-up (key start switch turned on). Leaving normal mode is done by: initiating a service operation with the keypad. See Service Operations section.

Service Operations

There are numerous VIDS service operations that can be initiated by the operator or service person. Each service operation is assigned a service program code (SPC). This service program code is entered into VIDS using the keypad. Entering the service program code initiates the corresponding service operation. Some of the service operations are:

Each service program code is a unique number of one to ten digits. The service program codes have a letter equivalent that describes the service operation. This letter equivalent makes it easier to remember the service program code for each operation. The English letter equivalent for each service program code is shown in parentheses. These codes are the same regardless of the on-board language.

After entering the service program code on the keypad it must be completed by pressing the OK key within five seconds after entering the last SPC character.

Show Acknowledged Events

Service program code: 3225 (EACK)

This service program code shows all active machine events and system faults that have been acknowledged but not corrected.

Show Event Statistics

Service program code: 37828 (ESTAT)

This service program code shows the number of system events and machine events since the main module memory was last cleared of all events (event list). Example:

Show Event List Contents

Service program code: 35478 (ELIST)

This service program code shows the event list in an abbreviated form. Event list entries are displayed on a last in - first out basis. "Out" represents when the event went deactive or turned off. This means some events may appear out of order based on their start times. Use the BACKWARD and FORWARD arrow keys to scroll through the list. The message "END OF LIST" is shown when the oldest event in the list is reached.

Machine Events

For each machine event in the event list, the following information is shown in the VIDS message area:

* Fault parameter name

* Fault parameter status

* Service meter reading when event began

Example: Machine event - sensor information

Example: Machine event - switch information

245.2 is the service meter reading when the event began. 000:04:13 is the duration of the event in HHH:MM:SS format.

When viewing a machine event, pressing the F1 key replaces what is shown on the second line of the message area with the fault parameter value and units. See F1 Key under the topic Keypad for additional information. Pressing the OK key puts the message center back in the previous mode.

System Events

For each system event in the event list, the following information is shown in the VIDS message area:

* Fault name

* Fault status

* Service meter reading when event began

Example: System event - sensor information

245.2 is the service meter reading when the event began. 000:04:13 is the duration of the event in HHH:MM:SS format.

When viewing a system event, pressing the F1 key replaces what is shown on the second line of the message area with MID, CID and FMI diagnostic information. See F1 Key under the topic Keypad for additional information.

The FORWARD and BACKWARD arrow keys are used to scroll through the event list.

Toggle Display Language

Service program code: 52 (LA)

This service program code toggles the information shown on the message area between two available languages. Information is shown in the selected language until the other language is selected.

Toggle Display Units

Service program code: 86 (UN)

This service program code toggles the data shown on the display, between U.S and Metric units of measure. Data is shown in the selected units until the other units are selected.

Clear Event List

Service program code: 25327255 (CLEARALL)

This service program code is used on machines with VIDS (wheel loaders) to clear the event list. In VIDS the event list can not be downloaded to be cleared, so as a result CLEARALL is used but is only active while viewing ELIST.

Machine Status

Service program code: 67828 (MSTAT)

NOTE: All screens are English only.

This service program code is used to view various sections of the machine status. The message area will show the version of the source code, configuration code, experiment number, and Information Builder version (ISB).

Pressing the right arrow key will allow other aspects of the machine status to be displayed (in the following order). They and their corresponding message area display are as follows:

* Hardware Version

* Model Number

* SERIAL NUMBER (MACHINE)

* Equipment Number

* Attachment Code

Used on large wheel loaders, to identify attachments on the machine.

* Language

* Configuration Type

* Operator ID

Enter Calibration Modes

Service program code: 7378 (SERV)

This service program code is used to access the calibration modes and procedures defined in VIDS. The left or right arrow can be used to scroll through the various calibration modes. The message display will show:

Other message area displays available are:

* TC IMPLR SOL - CAL

* TC PDL POS SNSR - CAL

NOTE: If OK is pressed, the phrase stays on display 15 seconds even if OK is pressed again.

Attachment Code

Service program code: 288224 (ATTACH)

This service program allows the operator to configure the attachment code for large wheel loaders (LWL). After "ATTACH" "OK" is entered from the keypad, the following is displayed:

The desired attachment code can then be entered from the keypad by entering the desired attachment code followed by "OK". If a valid attachment code has been entered, the following will be displayed:

If the same code is entered again, this code will be accepted as the new attachment code. If the same code is not entered at the second prompt as was at the first prompt, if an invalid code is entered at either prompt, or if "OK" was entered at either prompt (before entering a number) a new attachment code will not be accepted, leaving the old attachment code valid.

NOTE: The attachment code presently being used can be viewed through MSAT service program code (67828).

NOTE: The following chart lists the attachment codes for the 854G Wheel Tractor.