793F CMD Off-Highway Truck/Tractor Braking System Caterpillar

Electronic Control Module (ECM)

Usage:

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Illustration 1	g00554751
Electronic Control Module (ECM)

The "Brake ECM" determines responses based on the information from ECM inputs and information from memory. After the "Brake ECM" receives the information from inputs and information from memory, the "Brake ECM" will send a corresponding response through the outputs. The ECM input and outputs of the "Brake ECM" connect to the machine harness by two 70-pin connectors (J1 and J2).

Inputs

The machine has several input devices. The "Brake ECM" receives information from components about machine operations. The machine has inputs that are switch type and the machine has inputs that are sensor type. Switches provide signals to the switch inputs of the ECM. The possible outputs of a switch are listed: an open signal, a grounded signal and +battery signal. Sensors provide a signal to the ECM that has more than two states. The ECM inputs of the "Brake ECM" are listed in the table.

Outputs

The Brake ECM sends electrical signals to the outputs. The outputs can create an action or the outputs can provide information to the Transmission/Chassis ECM. The outputs for the Transmission/Chassis ECM are listed in the tables.

Input/Output

Each ECM uses the Cat Data Link to communicate with the other ECM on the machine. The data link is bidirectional. The data link allows the ECM to receive information. The data link allows the ECM to send information. The data link allows the sharing of information with other electronic control modules.

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Table 1
Brake ECM J1 Contact Descriptions
Pin	Description	Type
1	Key Switch (ON)	Switch Input
2	Engine Speed Sensor +	Input
3	Engine Speed Sensor -	Ground
4	Brake Cooling Pump Speed Sensor +	Input
5	Brake Cooling Pump Speed Sensor -	Ground
6	Engine Cooling Fan Speed Sensor +	Input
7	Engine Cooling Fan Speed Sensor -	Ground
9	Right Front Wheel Speed Sensor	Input
10	Cat Data Link (CDL) +	Input/Output
11	5 VDC Sensor Supply	Power
13	- Battery	Ground
14	AC Mode Switch Manual	Switch Input
16	Left Front Wheel Speed Sensor	Input
18	Rear Service Brake Pressure Sensor	Input
20	Cat Data Link (CDL) -	Input/Output
21	5 VDC Sensor Return	Ground
22	Sensor Passenger HVAC Outlet Temperature	Input
23	- Battery	Ground
24	AC Low Pressure Switch	Output
25	AC Mode Switch Auto	Output
26	ECM Location 0	Open
27	ECM Location 1	Ground
28	ECM Location 2	Open
29	Sensor Cab Temperature	Input
31	+ 24V Battery	Power
32	ECM Location Enable	Ground
33	ARC ON/OFF Switch (ON)	Input
35	Differential Filter Bypass	Input
36	Operator Temperature Control	Input
38	+ 24V Battery	Power
39	+ 24V Battery	Power
40	ARC ON/OFF Switch (OFF)	Input
43	TCS Test Switch	Input
44	8VDC Sensor Supply	Power
45	8VDC Sensor Return	Ground
46	+24 VDC Battery	Power
47	+24VDC Battery	Power
48	TCS Supply Solenoid	Output
49	Brake Cooling Pump Solenoid	Output
50	Prop Driver 1-4 Return	Ground
51	Engine Cooling Fan Solenoid	Output
54	Prop Drivers 11-12 Return	Ground
56	- Battery	Ground
57	- Battery	Ground
58	Rear Brake Solenoid (LH)	Output
59	RAXL Cooler Fan Solenoid	Output
60	Prop Drivers 5-8 Return	Ground
61	SEC Brake Solenoid	Output
62	Rear Brake Solenoid (RH)	Output
63	Service Brake Pressure Switch	Input
67	ARC Control Solenoid Rear	Output
68	ARC Control Solenoid Front	Output
69	10VDC Sensor Supply	Output
70	-Battery	Power

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Table 2
Brake ECM J2 Contact Descriptions
Pin	Description	Type
3	Brake Unloader Solenoid	Ground
5	RRAX Pump Unloader	Output
8	Solenoid Return	Ground
9	Brake Light Relay	Output
10	Compressor Clutch Relay	Output
13	Passenger Interlock (Powered Access Stairway Disable Relay)	Output
16	Left Park Brake Pressure Sensor	Input
17	Right Park Brake Pressure Sensor	Input
18	Secondary Brake Pedal	Input
21	Water Valve Actuator Signal	Input
22	Ground	Ground
23	Brake Cooler Filter Switch	Input
24	Retarder Lever	Input
26	Front Service Brake Pressure Sensor	Input
27	Brake Oil Temperature Sensor RH Rear	Input
30	Retard Machine Speed Increment	Input
31	Retard Machine Speed Decrement	Input
32	Brake Pump Pressure Sensor	Input
33	Right Rear Wheel Speed Sensor	Input
34	Left Rear Wheel Speed Sensor	Input
35	Secondary Brake Accumulator Pressure Sensor	Input
40	Brake Oil Temperature Sensor Left Rear	Input
41	Brake Oil Temperature Sensor Left Front	Input
42	Brake Oil Temperature Sensor Right Front	Input
43	Differential Lube Pressure Sensor	Input
49	Rear Differential Temperature Sensor	Input
50	Service Brake Accumulator Pressure Sensor/Switch	Input
51	Service Brake Pedal Sensor	Input
53	Brake Filter Bypass Switch	Input
56	CAN A Data Link +	Input/Output
57	CAN A Shield	Shield
63	Ground	Ground
64	CAN B + (SW PADS)	Input/Output
65	CAN B - (SW PADS)	Input/Output
66	CAN B Shield	Shield
67	CAN A + (J1939)	Input/Output
68	CAN A - (J1939)	Input/Output
69	CAN A Shield	Shield
70	CAN A - (J1939)	Input/Output