980H Wheel Loader Caterpillar

Power Train Electronic Control System

Usage:

980H PF8

The main functions of the power train electronic control system are as follows:

"Neutral Start Function"
"Manual Shift Function"
"Transmission Neutralizer Function"
"Parking Brake Function"
"Backup Alarm Function"
"Ride Control Function (If Equipped)"
"Diagnostic Operation"

Neutral Start Function

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Illustration 1	g00329538
Start Relay

The start relay is an output of the power train electronic control module (ECM). The start relay turns the start solenoid on and off. The start solenoid controls the starting motor. When the operator turns the key start switch to the START position and the power train ECM decides that all the starting conditions are satisfied, the power train ECM energizes the start relay with a +battery signal. The power train ECM will not allow the engine to be started unless the transmission direction control switch is in the NEUTRAL position. If the transmission direction control switch is in the NEUTRAL position, the power train ECM activates the start relay. The start relay allows the starting motor to turn. The power train ECM will not allow the starter to activate if the engine is running.

The start relay has a connector with two contacts. One contact receives power from connector contact J1-8 of the power train ECM. The other contact returns power to connector contact J2-3 of the power train ECM.

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

ReferenceFor more information on the key start switch, refer to the Service Manual module Systems Operation, "Switches" for the machine that is being serviced.

ReferenceFor more information on the power train electronic control module (ECM), refer to the Service Manual module Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.

Manual Shift Function

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Table 1
Modulating Valve (Transmission Clutch)
Fourth Speed Forward	3 and 2
Third Speed Forward	4 and 2
Second Speed Forward	5 and 2
First Speed Forward	6 and 2
Neutral	3
First Speed Reverse	6 and 1
Second Speed Reverse	5 and 1
Third Speed Reverse	4 and 1
Fourth Speed Reverse	3 and 1

Command Control Steering

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Table 2
Normal Shifting Sequence
Speed Range and Direction	REVERSE Position Transmission Shift	NEUTRAL Position Transmission Shift	FORWARD Position Transmission Shift	UP SHIFT Position Transmission Shift	DOWN SHIFT Position Transmission Shift
4F	4R	Neutral ⁽¹⁾ (4N)	No Change	No Change	3F
3F	3R	Neutral ⁽¹⁾ (3N)	No Change	4F	2F
2F	2R	Neutral ⁽¹⁾ (2N)	No Change	3F	1F
1F	1R	Neutral ⁽¹⁾ (1N)	No Change	2F	No Change
Neutral ⁽¹⁾ (1N, 2N, 3N, 4N)	Last ⁽²⁾	No Change	Last ⁽²⁾	Next ⁽³⁾	Prior ⁽³⁾
1R	No Change	Neutral ⁽¹⁾ (1N)	1F	2R	No Change
2R	No Change	Neutral ⁽¹⁾ (2N)	2F	3R	1R
3R	No Change	Neutral ⁽¹⁾ (3N)	3F	4R	2R
4R	No Change	Neutral ⁽¹⁾ (4N)	4F	No Change	3R

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^( 1 )	The speed and the direction that is shown in bold print is the gear readout.
^( 2 )	A directional shift out of neutral will cause a speed shift to the last speed that was selected in either forward or reverse.
^( 3 )	Speed shifts are allowed when neutral is selected. The gear readout will change the speed that is shown when neutral is selected and a speed shift is made. However, none of the solenoids are activated until forward or reverse is selected.

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Illustration 2	g03397207
(1) Transmission direction control switch (2) Transmission upshift switch (3) Transmission downshift switch

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Illustration 3	g03397204
Right Side of the Cab, Overhead (4) Transmission auto/manual switch (5) Manual position (6) Fourth speed position (7) Third speed position (8) Second speed position (9) First speed position (reverse)

Transmission auto/manual switch (4) tells the power train ECM of the desired shift mode, AUTO mode, or manual mode. The five position switch is also used to select the top speed for the transmission when the transmission is in the AUTO mode. In order to shift the transmission manually, the five position switch (4) must be in the MANUAL position (5). Shifting the transmission is the main function of the power train electronic control module (ECM). The power train ECM interprets the changes in the switch position. After the power train ECM interprets the changes in the switch position, the power train ECM shifts the transmission.

Transmission direction control switch (1) is located on the steering wheel. Transmission upshift switch (2) and transmission downshift switch (3) are located on the steering wheel. Transmission direction control switch (1) is a three-position switch that selects either forward, neutral, or reverse.

The operator selects a direction by moving transmission direction control switch (1) to one of three positions. Transmission direction control switch (1) tells the power train ECM of the desired direction of travel.

Transmission upshift switch (2) makes momentary contact in order to select the next higher speed. Transmission downshift switch (3) makes momentary contact in order to select the next lower speed. The operator selects a speed range by depressing transmission upshift switch (2) or by depressing transmission downshift switch (3). Transmission upshift switch (2) has two input connections at the power train ECM on connector J1. Transmission downshift switch (3) has two input connections to the power train ECM on connector J1.

Note: The correct status of the transmission upshift switch and of the transmission downshift switch is required. The correct status will allow the power train ECM to decide when the power train ECM should make each shift.

Note: The normally closed (N/C) circuit and normally open (N/O) circuit of the transmission downshift switch are used for diagnostic purposes. The normally closed (N/C) circuit and normally open (N/O) circuit of the transmission upshift switch are used for diagnostic purposes. If the normally closed (N/C) circuit and normally open (N/O) circuit are open at the same time, the power train ECM records a fault. If the normally closed (N/C) circuit and normally open (N/O) circuit are grounded at the same time, the power train ECM records a fault.

When the key start switch is turned from the OFF position to ON position, the power train ECM is activated. When the power train ECM is first activated, all of the clutch solenoid modulating valves are de-energized. The clutch solenoid modulating valves are de-energized regardless of the position of transmission direction control switch (1). The power train ECM then determines if transmission direction control switch (1) is in the NEUTRAL position. The power train ECM disables the transmission if the NEUTRAL position is NOT selected. If transmission direction control switch (1) is in the NEUTRAL position, the power train ECM selects the current speed and the current direction as neutral. The power train ECM activates the start relay when the key start switch is turned to the ON position. The power train ECM allows the engine to start if transmission direction control switch (1) is in the NEUTRAL position.

Note: Transmission direction control switch (1) must be in the NEUTRAL position when the key is turned to the START position. If transmission direction control switch (1) is not in the NEUTRAL position, the start relay will not be activated. For additional information on the neutral start function, refer to "Neutral Start Function".

ReferenceFor more information on the Caterpillar Monitoring System, refer to the Service Manual module Systems Operation, "Monitoring System (Power Train Functions)" for the machine that is being serviced.

ReferenceFor additional information on the transmission direction control switch, the transmission upshift switch, and the transmission downshift switch, refer to the Service Manual module Systems Operation, "Switches" for the machine that is being serviced.

ReferenceFor more information on the key start switch, refer to the Service Manual module Systems Operation, "Switches" for the machine that is being serviced.

Transmission Neutralizer Function

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Illustration 4	g03397298
(10) Transmission neutralizer limit switch

Left pedal position sensor (10) is located in the cab in the left brake pedal assembly. The left pedal position sensor is a pulse width modulated (PWM) sensor. The left pedal position sensor informs the power train ECM of the position of the left brake pedal. When the left brake pedal is depressed, the left pedal position sensor sends a PWM signal to the power train ECM. The power train ECM uses the PWM input in order to downshift the transmission. And, the power train ECM uses the PWM input in order to neutralize the transmission.

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Illustration 5	g03397299
Right Side of the Cab, Overhead (11) Transmission neutralizer override switch

Transmission neutralizer override switch (11) is an input of the power train ECM. The input signals to the power train ECM enable the transmission neutralizer or the input signals disable the transmission neutralizer. Transmission neutralizer override switch (11) is a momentary rocker switch.

Left pedal position sensor (10) signals the power train ECM to neutralize the transmission if the transmission neutralizer function is enabled. When the machine is started, the transmission neutralizer function is enabled. When the transmission neutralizer override switch (11) is depressed and released, the transmission neutralizer function is alternately enabled or disabled.

The transmission is neutralized by de-energizing the selected direction clutch solenoid. The selected speed clutch solenoid is still energized. The engine rpm will increase when the transmission is neutralized due to the no-load condition from the transmission. This condition allows full hydraulic power for bucket operation.

Note: When the transmission is neutralized, the speed/direction readout on the Caterpillar Monitoring System changes. The Caterpillar Monitoring System continues to show the speed that is selected but the direction will read neutral.

ReferenceFor more information on the left pedal position sensor, refer to the Service Manual module Systems Operation, "Sensors" for the machine that is being serviced.

ReferenceFor more information on the transmission neutralizer override switch, refer to the Service Manual module Systems Operation, "Switches" for the machine that is being serviced.

Parking Brake Function

The parking brake function prevents the operator from operating the machine while the parking brake is engaged. Driving through the parking brake causes accelerated wear to the friction materials of the parking brake.

When the parking brake control is disengaged, the transmission will shift normally. When the parking brake control is engaged, the transmission will not shift out of neutral to first speed forward or first speed reverse. If the transmission is in first speed forward or in first speed reverse and the parking brake is moved to the engaged position, the transmission will shift into neutral. If the transmission is in second speed forward or in third speed forward, the transmission will remain engaged.

The parking brake function activates a Warning Category 2 on the Caterpillar Monitoring System. The parking brake indicator will flash whenever the parking brake is engaged.

While the parking brake is engaged, Warning Category 2 will be activated. This condition will occur if the operator places the transmission direction control switch in the FORWARD position or the REVERSE position. The parking brake indicator will flash and the action light will flash.

When the parking brake is engaged and the transmission is in first speed, the power train ECM shifts the transmission to neutral. The power train ECM also sends the parking brake status to the Caterpillar Monitoring System via the CAT Data Link. When the parking brake is engaged, the alert indicator for the parking brake flashes on the Caterpillar Monitoring System. If the operator selects the FORWARD position or the REVERSE position and the parking brake is engaged, the Caterpillar Monitoring System initiates a Warning Category 2. A Warning Category 2 causes the parking brake indicator and the action lamp to flash. The action alarm will also sound.

ReferenceFor more information on the parking brake pressure switch, refer to the Service Manual module Systems Operation, "Switches" for the machine that is being serviced.

Driving Through the Parking Brake

The power train ECM will allow the operator to drive through the parking brake. The machine should be moved only for a short distance.

In order to drive through the parking brake, the operator must select first speed forward or first speed reverse. The operator must then move the transmission direction control switch to the NEUTRAL position. The operator must then move the transmission direction control switch to the previous direction that was selected.

Backup Alarm Function

The backup alarm function alerts surrounding personnel that the machine is backing up. The backup alarm is an output of the power train electronic control module (ECM). The power train ECM activates the backup alarm relay when the transmission direction control switch is in the REVERSE position. The backup alarm relay then activates the backup alarm. The backup alarm receives a +battery signal from the power train ECM when the backup alarm is activated.

The backup alarm has two terminals for electrical connections. One terminal receives power from connector contact J2-37 of the power train ECM. The other contact returns power to connector contact J2-3 and J1-7 of the power train ECM.

Ride Control Function (If Equipped)

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Illustration 6	g03397331
Right Side of the Cab, Overhead (12) Ride control switch

Ride control is an optional function that is enabled by a programmable parameter via the Caterpillar Electronic Technician (ET). Ride control can also be enabled by the calibration mode of the Caterpillar Monitoring System. Ride control is enabled when the operator places the ride control switch in the ON position or the AUTO position. In the ON position, ride control is activated at all times and the power train ECM continuously energizes the ride control solenoid. In the AUTO position, ride control is activated and ride control is deactivated. Ride control is activated when the machine ground speed increases above approximately 6 mph. Ride control is deactivated when the machine ground speed is below approximately 5.5 mph. When the ride control switch is in the AUTO position, the default speed is set to 6 mph. The default speed can be changed with the configuration screen of the Caterpillar Electronic Technician (ET). As ride control is activated and deactivated, the ride control solenoid is energized and de-energized.

The ride control system uses two ride control solenoids. The two ride control solenoids are outputs of the power train ECM. The ride control solenoids turn the ride control system on and off. When ride control is disabled, the number one ride control solenoid is de-energized and the number two ride control solenoid is energized. When ride control is enabled, the number one ride control solenoid is energized 5 seconds after the number two ride control solenoid is de-energized. The delay time can be changed with the "ride control equalization pressure time parameter" of the Caterpillar Electronic Technician (ET). Both of the ride control solenoids have a connector with two contacts. The number one ride control solenoid receives power from the connector contact J1-18 of the power train ECM. The number two ride control solenoid receives power from the connector contact J1-12 of the power train ECM. Both of the ride control solenoids return power to connector contact J2-3 of the power train ECM.

Diagnostic Operation

The power train electronic control module (ECM) detects faults that occur in most of the input circuits and the output circuits. A fault is detected when the signal at the contact of the power train ECM is outside a valid range. The power train ECM then records the fault. If the fault goes away, the fault information remains stored for future reference.

The diagnostics of the power train ECM are available to assist with the troubleshooting of detected faults. A service code is used to specify each fault. These service codes are shown in the display area of the Caterpillar Monitoring System. Service codes consist of three identifiers: MID, CID and FMI.

Module Identifier (MID) - The MID is a three-digit code that is shown on the display area. The MID is shown for approximately one second before the service code that is shown in the same area. The power train ECM that has diagnosed the fault is logged by the MID. The following examples are of some MID.

Module Identifier (MID) examples

Caterpillar Monitoring System ... 030

Power Train ECM ... 081

Implement ECM ... 082

Note: The MID of the power train control is 081. Make sure that the number 081 precedes the service code of the fault when you are troubleshooting the power train system. The Caterpillar Monitoring System also shows service codes of the faults that are not related to the power train system. MID 081 identifies the power train ECM as the source of the service code.

Component Identifier (CID) - The components that are faulty are noted by the CID. The following components are examples: start relay and reverse solenoid. The CID is a four-digit code that is shown on the display area. The CID and the FMI are shown together after the MID has been displayed.

ReferenceFor a list of the CID codes for the power train ECM, refer to the Service Manual module for Testing and Adjusting, RENR1625, "980H Wheel Loader Power Train", "Diagnostic Code List".

Failure Mode Identifier (FMI) - The FMI tells the type of failure that has occurred. The following situations are examples: voltage above normal, current below normal and abnormal frequency. The FMI is a two-digit code that is shown on the display area. The CID and the FMI are shown together after the MID has been displayed. A decimal point "." precedes the FMI.

ReferenceFor a list of the FMI codes for the power train ECM, refer to the Service Manual module for Testing and Adjusting, RENR1625, "980H Wheel Loader Power Train", "Diagnostic Code List".

The power train ECM does not have a display area for displaying diagnostic information to service personnel. Diagnostic information concerning the power train system is sent on the CAT Data Link to the Caterpillar Monitoring System. Service personnel must be familiar with the Caterpillar Monitoring System in order to troubleshoot the power train system.

The service mode of the Caterpillar Monitoring System allows service personnel to see the faults that were detected by the power train ECM. The service mode of the Caterpillar Monitoring System allows service personnel to troubleshoot the faults that were detected by the power train ECM. While the Caterpillar Monitoring System is in the service mode, the service code for any detected fault of the power train electronic control system is shown in the display area of the Caterpillar Monitoring System.

When the service mode is first entered, all service codes for any detected faults scroll in the display area. For troubleshooting and clearing, the particular service code must be placed on hold. The display area continuously alternates between showing the MID, and then showing both the CID and the FMI of the particular service code for the fault that is on hold.

The Caterpillar Monitoring System enters service mode when ground is removed from the service input and the clear input. The mode number 3 for service mode is shown in the display area of the Caterpillar Monitoring System. To place a service code for a fault on hold, ground the service input. To clear a service code for a fault on hold, ground the clear input. The Caterpillar Monitoring System exits service mode when ground is added to the service input and the clear input.

Note: The time that is needed to clear a fault and the time that is needed to set a fault can last less than 1 second up to 60 seconds.

ReferenceFor more information on the Cat Data Link, refer to the Service Manual module Systems Operation, "Cat Data Link" for the machine that is being serviced.

ReferenceFor more information on troubleshooting the power train ECM, refer to the Service Manual module Testing and Adjusting, RENR1625, "980H Wheel Loader Power Train".

ReferenceFor more information on troubleshooting the power train electronic control system, refer to the Service Manual module Testing and Adjusting, RENR1625, "980H Wheel Loader Power Train".

Note: The Service Manual module Systems Operation, Testing and Adjusting, SENR1394, "Caterpillar Monitoring System" should only be used as a reference to the display of the faults of the power train electronic control system. Use the Service Manual module Testing and Adjusting, RENR1625, "980H Wheel Loader Power Train" in order to troubleshoot the faults of the power train electronic control system.