992K Wheel Loader Caterpillar

Electronic Control (Power Train System)

Usage:

992K KK2

Electronic Control Module (ECM)

The Power Train ECM is located inside the right-hand side of the cab enclosure. The Power Train ECM is positioned next to the Implement ECM.

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Illustration 1	g00785019
Power Train ECM

The Power Train ECM shifts the transmission. The transmission direction control switch sends the operator input to the Power Train ECM. The operator input indicates the desired speed for the transmission and the desired direction for the transmission. Decisions are made by the Power Train ECM based on the input information. Decisions are also made by the Power Train ECM based on information within the ECM memory. After the Power Train ECM receives the input information and the information from memory, the Power Train ECM sends a corresponding response via the outputs.

Input

The machine has several input devices. Input devices inform the Power Train ECM of the operating conditions of the machine. The switch input and the sensor input are used by the machine. The switch input of the Power Train ECM is provided with the following signals from the switches: an open, a ground and a +battery. Sensors provide a constantly changing signal to the Power Train ECM. Refer to Table 1 and Table 2.

Outputs

The Power Train ECM responds to decisions by sending electrical signals through the outputs. The outputs can create an action or the outputs can provide information to the Power Train ECM. Table 1 and Table 2 list the outputs for the Power Train ECM.

Input/Output

The Cat Data Link is used to communicate with the other electronic control modules on the machine. The Cat Data Link is bidirectional. This system allows the Power Train ECM to receive information and the Power Train ECM also sends information. The Cat Data Link allows the sharing of information with other electronic controls.

The Power Train ECM receives the product ID from Advisor. This helps the Power Train ECM to identify the machine model.
The Power Train ECM sends the following information to the Cat Monitoring System: engine speed, machine ground speed, parking brake switch status, transmission speed selection, transmission direction selection and service code of the transmission.
The monitoring system displays this information for the operator or for service personnel.

A module identifier (MID) is assigned to all of the electronic controls that use the Cat Data Link. The MID for the Power Train ECM is 081.

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Table 1
Contact Description for the Power Train ECM J1
No.⁽¹⁾	Function
1	Keyswitch On
2	Transmission Output Speed Sensor 1+
3	Transmission Output Speed Sensor 1 -
4	Transmission Output Speed Sensor 2 +
5	Transmission Output Speed Sensor 2 -
8	Engine Speed Tach +
9	Engine Speed Tach -
10	CAT Data Link +
11	+5V Sensor Power
12	Parking Brake Solenoid
13	Unswitched Battery -
15	Transmission Input Speed Sensor +
16	Transmission Input Speed Sensor -
18	Torque Converter Output Speed Sensor (994 Only)
20	Cat^® Data Link -
21	5V Sensor Return
22	Autolube Grease Level Sensor
23	- Unswitched Battery
26	ECM Location Code 1(Open)
27	ECM Location Code 2(Ground)
28	ECM Location Code 4(Open)
29	Transmission Oil Temp Sensor
30	Torque Converter Oil Temp Sensor
31	+ Unswitched Battery
32	ECM Location Code Enable (Ground)
33	Steering/Transmission Lock Switch (N/C)
34	Steering/Transmission Lock Switch (N/O)
36	Autolube Pump Pressure Sensor
37	Autolube NEEF Pressure Sensor
38	+ Unswitched Battery
39	+ Unswitched Battery
40	Upshift Switch (N/C)
41	Upshift Switch (N/O)
42	Downshift Switch (N/C)
43	Downshift Switch (N/O)
44	+ 8V Supply
45	- 8V Return
49	Clutch #4 (Speed 2)
50	PWM Driver Return (01-04)
51	Clutch #5 (Speed 1)
52	Autolube Solenoid
53	Fuel Level Sender Analog (992/854 Only)
55	PWM Driver Return (09-12)
57	– Unswitched Battery
58	Lockup Clutch Solenoid
59	Impeller Clutch Solenoid
60	PWM Driver Return (05-08)
61	Axel Oil Cooler Solenoid (994K Only)
62	Clutch #2 (Forward Solenoid)
63	Autolube Grease Low Level Switch (844)
63	Transmission Right Oil Filter Bypass Switch (994)
64	Transmission Filter Bypass Switch (844/854/990/992/993)
64	Transmission Left Oil Filter Bypass Switch (994)
65	Clutch #1 (Reverse)
66	Clutch #3 (Speed 3)
69	+10 V Supply
70	– Unswitched Battery

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⁽¹⁾	The connector contacts that are not listed are not used. The connector has 70 contacts.

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Table 2
Contact Description for the Power Train ECM J2
No.⁽¹⁾	Function
1	Keyswitch Start
2	Axle Oil Cooler Solenoid (844/854/990/992)
3	Main Relay
4	Solenoid Return
5	Ride Control Solenoid (992 Only)
6	Machine Power Distribution Relay
7	Start Relay
8	Solenoid Return
9	Powered Access Disable Relay (994 Only)
10	Heated Mirror Relay
11	Machine Feature Alarm
12	Autolube Manual Lube (844 Only)
13	Bumper Transmission Lockout LED
17	Impeller Clutch Pressure Sensor
19	Backlight Dimmer
20	Backup Alarm Relay
23	Direction Sw (Neutral)
25	Ambient Air Temp (994H Only)
26	Front Axle Oil Temperature Sensor
27	Rear Axle Oil Temperature Sensor
28	Direction Switch (Reverse)
31	Powered Access Position Switch (N/O)
32	Front Brake Lube Oil Pressure Switch ( 993/994)
33	Rear Brake Lube Oil Pressure Switch ( 993/994)
34	Brake Charge Pressure Sensor
35	Torque Converter Pedal Sensor
37	Park Brake Operator Switch (N/O)
38	Park Brake Operator Switch (N/C 1)
39	Park Brake Operator Switch (N/C 2)
41	Park Brake Oil Pressure
42	Front Service Brake Pressure Sensor
43	Rear Service Brake Pressure Sensor
44	Bumper Transmission Lockout (N/C)
45	Autolube Pressure Fault Switch (844 Only)
45	Transmission Oil Full Level Switch (994K)
47	Bumper Transmission Lockout (N/O)
49	Direction Switch (Forward)
50	Fuel Level Sender
54	LH Armrest Switch (N/O)
55	LH Armrest Switch (N/C)
56	CAN A High
58	Transmission Oil Low Level Switch
59	Powered Access Position Switch (N/C) (994 Only)
61	Operator Seat Belt Switch (N/O)
62	Operator Seat Belt Switch (N/C)
64	CAN B High
65	CAN B Low
67	CAN A High
68	CAN A Low
70	CAN A Low

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⁽¹⁾	The connector contacts that are not listed are not used. The connector has 70 contacts.

Electrical Input Components

Switches

STIC Control

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Illustration 2	g01444766

Upshift

The upshift switch tells the ECM that the operator wants the transmission to upshift one gear. The ECM will log a diagnostic code of CID 0622 for the switch.

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Table 3
Switch Status
Position	Normally Open	Normally Closed
Depressed	Closed	Open
Released	Open	Closed

Downshift

The downshift switch tells the ECM that the operator wants the transmission to downshift one gear. The ECM will log a diagnostic code of CID 0621 for the switch.

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Table 4
Switch Status
Position	Normally Open	Normally Closed
Depressed	Closed	Open
Released	Open	Closed

Direction

The direction switch has three positions: forward, neutral and reverse. The operator selects the direction of the transmission through the switch. The ECM will log a diagnostic code of CID 0623 for the switch.

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Table 5
Switch Status
Position	Reverse	Neutral	Forward
Reverse	Closed	Open	Open
Neutral	Open	Closed	Open
Forward	Open	Open	Closed

Transmission Oil Filter Bypass

Informs the Power Train ECM when the transmission oil filter is restricted.

Transmission Oil Level

Informs the Power Train ECM when the transmission oil level is low.

Parking Brake Position

The parking brake cab position switch indicates that the operator wants to engage or disengage the parking brake.

Accumulator Pressure

The brake accumulator pressure switch has one input. This feature outputs the status and position of the brake accumulator pressure switch.

Powered Access Stairway Position

Powered Access Stairway Position indicates whether the stairway is raised or lowered.

Steering and Transmission Lock

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Illustration 3	g01444768

The switch tells the ECM when the operator has the lock lever in the locked position. The ECM will log a diagnostic code of CID 0626 for the switch.

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Table 6
Switch Status
Switch Position	Normally Open	Normally Closed
Locked	Closed	Open
Unlocked	Open	Closed

Parking Brake

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Illustration 4	g01444770

The operator uses the parking brake switch in order to set the brake. The ECM sets the brake if the operating conditions of the machine are appropriate. The ECM will log a diagnostic code of CID 0070 for the switch.

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Table 7
Switch Status
Switch Position	Normally Open	Normally Closed
Out	Closed	Open
In	Open	Closed

Parking Brake Pressure

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Illustration 5	g01444773

The parking brake pressure switch provides the ECM with information about the hydraulic portion of the parking brake assembly. The parking brake is applied by a spring. The parking brake is released by hydraulic pressure. The parking brake is ON when the pressure switch is not actuated. The parking brake is OFF when the pressure switch is actuated. The ECM will log a diagnostic code of CID 0627 for the switch.

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Table 8
Switch Status
Switch Position	Normally Open	Normally Closed
High Pressure	Closed	Open
Low Pressure	Open	Closed

Lockup Clutch (Attachment)

(7) Lockup Clutch (Keypad)

The switch tells the ECM that the operator wants to enable the lockup clutch. The switch tells the ECM that the operator wants to disable the lockup clutch.

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Table 9
Switch Status
Switch Position	Normally Open
On	Closed
Off	Open

Ride Control (Attachment) (992K Only)

The ride control switch tells the ECM that the operator has selected a mode. The ECM will log a diagnostic code of CID 0367 for the switch.

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Table 10
Switch Status
Switch Position	Switch 2	Switch 1
On	Ground	Open
Off	Ground	Ground
Auto	Open	Ground

Quickshift

The switch tells the ECM when the operator selects the quickshift function. The ECM will log a diagnostic code of CID 0628 for the switch.

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Table 11
Switch Status
Switch Position	Normally Open	Normally Closed
On	Closed	Open
Off	Open	Closed

Reduced Rimpull

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Illustration 6	g02731213

The Power Train ECM reduces rimpull by increasing the current to the impeller clutch solenoid, which reduces the hydraulic pressure to the impeller clutch and allows slippage between the impeller and the torque converter housing. By additionally decreasing the impeller clutch pressure, the impeller will slip more, resulting in lower torque to the power train. The resulting additional engine horsepower can be used for the implements. Each time the reduced rimpull control switch on the keypad is pressed, the maximum allowable rimpull percentage is reduced. The LED lamps above the switch indicate the current rimpull setting. There are four settings as shown in this image. Three illuminated LEDs indicate full maximum allowable rimpull (HIGH), which is the default setting. The rimpull settings are:

Switch not pressed = HIGH or 100% (three LEDs ON)
Switch pressed once = MED-HIGH or 90% (two LEDs ON)
Switch pressed twice = MED-LOW or 80% (one LED ON)
Switch pressed three times = LOW or 70% (LEDs OFF)

Note: The 854 rimpull control strategy also limits the engine speed at the reduced rimpull settings.

The switch allows the operator to select one of the four levels that are available for rimpull. The ECM will log a diagnostic code of CID 0138 for the switch.

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Table 12
Switch Status
Switch Position	#1	#2	#3	#4
Large Dot	Ground	Open	Open	Open
Third Dot	Open	Ground	Open	Open
Second Dot	Open	Open	Ground	Open
Small Dot	Open	Open	Open	Ground

Transmission Lockout (Ground Level)

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Illustration 7	g01444783

The switch locks out the transmission with a padlock as a safety measure. The switch is located at the service center on the bumper. The ECM will log a diagnostic code of CID 0348 for the switch.

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Table 13
Switch Status
Switch Position	Normally Open	Normally Closed
On	Closed	Open
Off	Open	Closed

Heated Mirror (Attachment)

The switch activates the function for the heated mirror for five minutes. During the five minutes, any additional pressing of the switch will be ignored. The timer for the heated mirror cannot be stopped. The timer for the heated mirror cannot be restarted.

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Table 14
Switch Status
Switch Position	Normally Open
Momentarily On	Closed
Off	Open

Sensors

Transmission Input Speed

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Illustration 8	g01445489

The transmission input speed sensor tells the ECM the speed of the input shaft of the transmission. The ECM will log a diagnostic code of CID 0672 for the transmission input speed sensor.

Transmission Output Speed

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Illustration 9	g01445492

The transmission output speed sensors detect the speed in the output shafts in the drop box of the transmission. Information about the transmission output speed is broadcast on the Cat data link. Two sensors are required for detecting directional changes in order to ensure accurate clutch slippage for engaging the impeller clutch. Diagnostic codes that are associated with the output speed sensors will remain active until a valid transmission output speed is detected on the failed sensor. The ECM will log a diagnostic code of CID 0585 for the first transmission output speed sensor. The ECM will log a diagnostic code of CID 0673 for the second transmission output speed sensor.

Position of Torque Converter Pedal

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Illustration 10	g01445493

The pedal position sensor determines the position of the torque converter pedal. The sensor sends a PWM signal to the ECM. The ECM monitors the signal. Then, the ECM calculates the position of the pedal from the signal. Information about the transmission output speed is broadcast on the Cat data link. The ECM will log a diagnostic code of CID 1712 for the torque converter pedal position sensor.

Impeller Clutch Pressure

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Illustration 11	g01445500

The sensor determines the pressure of the impeller clutch. The sensor sends a PWM signal to the ECM. The ECM monitors the signal. Then, the ECM calculates the pressure from the signal. Information about the impeller clutch pressure is broadcast on the Cat data link. The ECM will log a diagnostic code of CID 0603 for the torque converter pedal position sensor.

Autolube Pressure

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Illustration 12	g01445502

The sensor determines the pressure of the auto lubrication system. The sensor sends a signal to the ECM. The ECM monitors the signal. Then, the ECM calculates the pressure from the signal. The ECM will log a diagnostic code of CID 0379 for the autolube pressure sensor.

Grease Level for Autolube

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Illustration 13	g01445503

The sensor determines the level of grease in the auto lubrication system. The sensor tells the ECM the amount of grease that is available. The sensor is an analog sensor. The sensor is composed of a rod and ten resistors that are controlled by switches. A float travels along the rod. As the float moves down the rod, the float passes below a switch. The switch opens and the associated resistor is added in series to the total resistance. The grease level is full when all of the switches are closed. The grease level is low when all of the switches are open. The ECM will log a diagnostic code of CID 1022 for the autolube grease level sensor.

Transmission Oil Temperature

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Illustration 14	g01445505

The sensor monitors the oil temperature at the inlet of the transmission control. The temperature is used in order to calibrate the impeller clutch. The temperature must be above 40 °C (104 °F). The ECM will log a diagnostic code of CID 0177 for the oil temperature sensor.

NEEF Autolube Pressure

The Auto Lube (NEEF) Pressure sensor is an input of the ECM. The purpose of the sensor is to tell the ECM the grease pressure of the Auto Lube system at a point between the pump and the injectors.

Axle Oil Temperature (Front/Rear)

The ECM calculates the respective Axle Oil Temperature from the duty cycle signal of the sensor.

Brake Oil Pressure (Front/Rear)

The ECM calculates the respective Brake Oil Pressure from the duty cycle signal of the sensor.

Fuel Level

The ECM calculates the fuel level from the raw duty cycle signal of the sensor. This is part of the fluid level monitoring feature.

Torque Converter Out Pressure Sensor

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Illustration 15	g01445506

The sensor monitors the transmission pump pressure (P1).

Transmission Pressure

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Illustration 16	g01445506

The sensor monitors the transmission pump pressure. The ECM will log a diagnostic code of CID 0862 for the pump pressure sensor.

Wire for Tachometer

The Engine ECM drives the frequency for this input. The frequency is related to the actual engine rpm. The ECM will log a diagnostic code of CID 0190 for the engine speed sensor.

Electrical Output Components

Solenoids

Transmission Clutch Solenoids

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Illustration 17	g01444279

The clutch solenoid valves are outputs of the Power Train Electronic Control Module (ECM). The purpose of the solenoid valve is to direct pilot oil to the ends of the control spool. The control spool will shift. This solenoid allows pressure oil to flow to the corresponding clutches. The Power Train ECM activates the appropriate solenoid valve for the required clutches for the speed and for the direction that has been selected.

Clutches 1 and 2 are for direction. Clutches 3, 4, and 5 are for speed.

In order for the machine to move, one speed clutch solenoid and one direction clutch solenoid must be activated. When the transmission is in neutral, only clutch solenoid valve 3 is activated. When the transmission is neutralized, the solenoid for the direction clutch is deactivated. Only the speed clutch solenoid is activated. The clutch solenoid valve is energized by a PWM signal that is sent by the Power Train ECM.

The solenoids engage the speed clutches and direction clutches in the transmission. The ECM will log a diagnostic code of CID 1401 for the first clutch solenoid. The ECM will log a diagnostic code of CID 1402 for the second clutch solenoid. The ECM will log a diagnostic code of CID 1403 for the third clutch solenoid. The ECM will log a diagnostic code of CID 1404 for the fourth clutch solenoid. The ECM will log a diagnostic code of CID 1405 for the fifth clutch solenoid.

Note: The solenoid coils are not designed for 24 V operation. The Power Train ECM sends a 24 V PWM signal at a duty cycle which provides an average voltage of 12 V to the solenoid coils. Do NOT activate the coils with 24 VDC. The life of the coils will be drastically reduced.

Ride Control Solenoid (992K Only)

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Illustration 18	g01444280

The ride control system uses one solenoid valve. The solenoid valve activates and the solenoid valve deactivates the ride control system. The ride control solenoid is an output of the transmission Electronic Control Module (ECM). The ride control solenoid has a connector with two contacts. One contact receives power from the connector contact J1-18 of the Power Train ECM. The other contact returns power to the connector contact J2-5 of the Power Train ECM. The ECM will log a diagnostic code of CID 0363 for the ride control solenoid.

Torque Converter Impeller Clutch Solenoid

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Illustration 19	g01444281

The impeller clutch solenoid valve is an output of the ECM and functions as a reducing valve. The solenoid valve modulates 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 ECM will log a diagnostic code of CID 0678 for the impeller clutch solenoid.

Torque Converter Lockup Clutch Solenoid (Attachment)

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Illustration 20	g01444286

The solenoid functions as a proportional valve. The solenoid modulates hydraulic pressure to the lockup clutch. The ECM increases the current to the solenoid valve and the hydraulic pressure at the lockup clutch is increased. The ECM decreases the current to the solenoid valve and the hydraulic pressure at the lockup clutch is at a minimum. The ECM will log a diagnostic code of CID 0679 for the lockup clutch solenoid.

Autolube Solenoid (Attachment)

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Illustration 21	g01444287

The solenoid activates the autolube pump. The solenoid deactivates the autolube pump. The ECM will log a diagnostic code of CID 0378 for the autolube solenoid.

Axle Oil Cooler Bypass Solenoid

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Illustration 22	g01483775

When the bypass solenoid is de-energized, pilot flow is sent through the axle oil cooling motor, driving the axle oil cooling pumps and axle oil cooling flow. When the solenoid is energized, the pilot flow to the axle oil cooling motor is diverted, and no oil is pumped through the axles. The ECM will log a diagnostic code of CID 2825 for the axle oil cooler bypass solenoid.

Relays

Start Relay

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Illustration 23	g01444289

The relay is used in order to energize two other start relays. One of the relays energizes the start solenoids. The other relay energizes the starting motor. The ECM will log a diagnostic code of CID 0444 for the start relay.

Relay for Heated Mirror (Attachment)

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Illustration 24	g01444289

The relay is used in order to activate the function for the heated mirror for 5 minutes. This relay is driven by a sinking driver. The relay for the heated mirror does not have a diagnostic.

Backup Alarm Relay

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Illustration 25	g01444289

The backup alarm relay is driven by the ECM. The relay activates two backup alarms. The backup alarm warns nearby personnel that the transmission of the machine is in the reverse gear. The two backup alarms sound whenever the direction switch is in the reverse position. An open in the circuit for the relay does not cause a diagnostic code. The ECM will log a diagnostic code of CID 0144 for the backup alarm relay.

Main Power Relay

The main power relay is part of the battery management feature. This relay controls the switch power distribution. This switch provides the key switch input to Implement ECM, Advisor, Messenger, Indication module and CAES. This switch also turns off other components such as HVAC and Wipers. The machine ECM shall turn the main power relay on and off based on the key switch position.

When the key switch transitions from OFF to ON, the main power relay shall be energized immediately
When the key switch transitions from ON to OFF, the main power relay shall be de-energized immediately.

The Machine ECM shall turn the main power relay off 5 minutes after the occurrence of an Automatic Idle Shutdown. This delay time shall be configurable through a development tool at run time.

Machine Power Distribution Relay

The machine power distribution relay is part of battery management. It provides battery+ power to the Engine ECM, Implement ECM, Advisor, Messenger, Indication Module and CAES. The Power Train ECM shall turn off the machine power distribution relay 30 minutes after the main power relay has been turned off.

Powered Access Disable Relay

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Illustration 26	g01444289

This relay is part of the powered access feature. This relay prevents the powered access from operating unless the following is true:

The Transmission is in NEUTRAL
The Parking Brake is ON

Indicators

Ground Level Transmission Lockout

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Illustration 27	g01458802

The LED is used to indicate that the ground level transmission lockout is active. The indicator emits an amber colored light. The indicator requires 24 VDC in order to function properly. The indicator is active when the current is between 8 mA and 16 mA. The indicator is not active when the current is between 0 mA and 8 mA. This component is not a push-to-test LED.

Data Link

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Illustration 28	g06155907
Connections of the Cat Data Link

The Cat Data Link is a communication link that is used for the movement of data between electronic controls. The Cat Data Link allows communication between the Power Train electronic control module (ECM) and all other ECMs. The Cat Data Link is bidirectional. The Cat Data Link allows the Power Train ECM and other ECMs to input information and to output information. The Cat Data Link is not a visible component. The Cat Data Link consists of the following parts: internal circuits for Power Train ECM, the related harness wiring and the service tool connector. The Cat Data Link and the Power Train ECM are connected at pin-out J1-10 and pin-out J1-20.

The Power Train ECM uses data that is sent back and forth on the Cat Data Link. The following information is some of the information that is shared:

The Power Train ECM receives a service command from the Advisor in order to change the operating modes of the Power Train electronic control system. The service command can direct the Power Train ECM to read service codes that are stored in the ECM memory..
The Power Train ECM sends signals to the Advisor. The Advisor uses the signals to report on the status of the Power Train electronic control system. The Advisor alerts the operator of the status by illuminating the corresponding alert indicator.
The Power Train ECM sends the parking brake status to Advisor. The Power Train ECM sends the direction of the transmission to Advisor. The Power Train ECM sends the status of transmission speed to Advisor. Advisor uses this information to display the direction of the transmission and the speed of the transmission. Advisor uses this information in order to show the operator if the parking brake is engaged or disengaged.

Note: All electronic control modules that use the Cat Data Link have a module identifier (MID). These module identifiers are used on the 992K Wheel Loader and 854K Wheel Dozer:

Module Identifiers (MID)

Engine ECM ... 036

Messenger ... 052

Advisor ... 053

Power Train ECM ... 081

Implement ECM ... 082

VIMS ... 161