938H Wheel Loader and IT38H Integrated Toolcarrier Power Train Caterpillar

Electronic Control Module

Usage:

938H JKM

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Illustration 1	g01420309
Power Train Electronic Control Module (ECM) (1) Connector J1. (2) Connector J2.

The power train electronic control module (ECM) is located on the back wall of the cab to the right of the operator's station. The power train ECM shifts the transmission. The operator input indicates the desired speed for the transmission and the desired direction for the transmission. The power train ECM makes decisions that are based on the input information and on the memory information. After the power train ECM receives the input information and the memory information, the power train ECM sends a corresponding response via the outputs. The inputs and outputs of the power train ECM are connected to the machine harness. Use contact connectors J1 and J2.

Inputs

The machine has several input devices. Input devices inform the power train ECM of the operating conditions of the machine. The machine has inputs from switches and sensors. Switches provide an open, a ground or a +battery to the inputs of the implement ECM. Sensors provide a constantly changing signal to the power train ECM. The inputs into the implement ECM are listed in the tables that follow.

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. The outputs for the implement ECM are listed in the tables that follow.

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 allows the power train ECM to receive information and this allows the power train ECM to send information. The CAT Data Link allows the sharing of information with other electronic controls.

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.

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

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Table 1
J1 Connector (Power Train ECM)
No.	Function	Type
1	Keyswitch ON	Switch Input
2	Transmission output speed sensor (A)+	Frequency Input
3	Transmission output speed sensor (A)-	Frequency Input
4	Transmission output speed sensor (B)+	Frequency Input
5	Transmission output speed sensor (B)-	Frequency Input
6	Intermediate speed sensor (A)+	Frequency Input
7	Intermediate speed sensor (A)-	Frequency Input
8	Intermediate speed sensor (B)+	Frequency Input
9	Intermediate speed sensor (B)-	Frequency Input
10	Cat Data Link (+)	Data Link
11	Unused ⁽¹⁾	-
12	Backup Alarm	Solenoid Output
13	Battery 1 (-)	Ground
15	Torque Converter Output Speed Sensor (+)	Frequency Input
16	Torque Converter Output Speed Sensor (-)	Frequency Input
20	Cat Data Link (-)	Data Link
22	Transmission oil temperature sensor	Sensor input
23	Battery 2 (-)	Ground
29	Fuel level sender	Sensor input
30	Hydraulic temperature sender	Sensor input
31	Battery 1 (+)	Power
33	Auto/Manual Switch Auto 4	Switch Input
34	Auto/Manual Switch (MANUAL)	Switch Input
35	Auto/Manual Switch Auto (1-4)	Switch Input
36	Primary steering pressure sensor	Sensor input
37	Secondary steering pressure sensor	Sensor input
39	Battery 2 (+)	Power
40	First Gear Switch	Switch Input
41	Second Gear Switch	Switch Input
42	Third Gear Switch	Switch Input
43	Fourth Gear Switch	Switch Input
44	Sensor Power Supply (+8V)	Power
45	Sensor Return (+8V)	Sensor Return
47	Battery 3 (+)	Power
48	Clutch 6 (First Gear)	Solenoid Output
49	Clutch 5 (Third Gear)	Solenoid Output
50	Return for Speed 1-3 Clutches	Solenoid Return
51	Clutch 4 (Second Gear)	Solenoid Output
52	Implement pressure reduction solenoid	Solenoid Output
53	Rear axle temperature sensor	Sensor input
55	Return for forward low, reverse, LUC, and AUX float detent	Solenoid Return
57	Battery 3 (-)	Ground
58	Differential lock actuation solenoid	Solenoid Output
59	Front differential lock solenoid	Solenoid Output
60	Return for Forward Clutch	Solenoid Return
61	Rear differential lock solenoid	Solenoid Output
62	Clutch 2 (Forward high)	Solenoid Output
63	Implement pod downshift switch (N/O).	Switch Input
64	Transmission oil filter bypass switch	Switch Input
65	Clutch 3 (Reverse)	Solenoid Output
66	Clutch 1 (Forward low)	Solenoid Output
67	Lift/tilt detent magnet solenoid	Solenoid Output
68	Cooling demand fan solenoid	Solenoid Output

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^( 1 )

All other pins that are not listed are also unused.

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Table 2
J2 Connector (Power Train ECM)
No.	Function	Type
1	Keyswitch (Start)	Switch Input
2	Rear axle cooler solenoid	Solenoid Output
3	Aux/Float detent magnet solenoid	Solenoid Output
4	Axle cooler solenoid and ride control return	Return
5	Ride control solenoid 1 (ON/OFF)	Solenoid Output
6	Ride control solenoid 2 (ON/OFF)	Solenoid Output
7	Start relay	Solenoid Output
8	Start relay return and Backup alarm return	Return
9	Secondary steering intermediate relay	Solenoid Output
10	Heated mirror relay	Solenoid Output
11	Unused ⁽²⁾	-
15	Left front wheel speed A	Sensor Input
16	Left front wheel speed B	Sensor Input
17	VSC 3 (Power)	Sensor Input
18	Left pedal position sensor	Sensor Input
23	Transmission direction control switch (Neutral)	Switch Input
24	Right front wheel speed B	Sensor Input
25	Right front wheel speed A	Sensor Input
26	Right rear wheel speed B	Sensor Input
27	Right rear wheel speed A	Sensor Input
28	Transmission direction control switch (Reverse)	Switch Input
29	Heated mirror switch	Switch Input
30	Transmission override switch	Switch Input
31	Neutralizer disable switch	Switch Input
32	Hold for lift pressure	Sensor Input
33	Variable shift control (Mid Range)	Sensor Input
34	Left rear wheel speed A	Sensor Input
35	Left rear wheel speed B	Sensor Input
36	Secondary steering test switch	Switch Input
37	Primary steering pressure switch (N/O)	Switch Input
38	Primary steering pressure switch (N/C)	Switch Input
39	Implement detent enable switch	Switch Input
40	Secondary steering pressure switch (N/O)	Sensor Input
41	Forward/Neutral/Reverse Input 3 (Lever machines)	Sensor Input
42	Remote Forward/Neutral/Reverse Neutral (Joystick) or Forward/Neutral/Reverse Input 4 (Lever machines)	Sensor Input
43	Remote Forward/Neutral/Reverse Forward (Joystick) or Forward/Neutral/Reverse Input 6 (Lever machines)	Sensor Input
44	Hydraulic filter bypass switch	Switch Input
45	Ride control switch (AUTO)	Switch Input
46	Ride control switch (ON)	Switch Input
47	Low brake oil pressure switch	Switch Input
48	Articulation angle sensor	Sensor Input
49	Transmission direction control switch (Forward)	Sensor Input
50	Front axle oil temperature switch	Sensor Input
51	Torque converter temperature sensor	Sensor Input
52	Parking brake switch (Engaged)	Switch Input
53	Parking brake switch (Disengaged)	Switch Input
54	Differential lock switch (N/O)	Switch Input
55	Differential lock switch (N/C)	Switch Input
56	CAN A +	Data link
58	Remote Forward/Neutral/Reverse Forward	Switch Input
59	Remote Forward/Neutral/Reverse Neutral	Switch Input
60	Remote Forward/Neutral/Reverse Reverse	Switch Input
61	Secondary steering pressure switch (N/C)	Switch Input
62	Case drain filter switch (N/C)	Switch Input
67	CAN A +	Data link
68	CAN A -	Data link
70	CAN A -	Data link