HARNESS AS-ENGINE 4366946 - Caterpillar

System OperationThe PWM sensors provide a signal to the engine's ECM. The sensors receive a 8.0 0.4 VDC regulated voltage from the ECM.The sensor's wires are routed from the ECM to the sensor connectors. The following list gives the terminal locations for the sensor connector.
Terminal A 8 V supply
Terminal B sensor return
Terminal C sensor signalThe ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.
Illustration 1 g01383855
Typical schematic
Illustration 2 g01444508
Location of the ECM connectors (1) J2/P2 ECM connectors (2) J1/P1 ECM connectors
Illustration 3 g01213937
P1 ECM connector (P1-4) 8 V supply (P1-5) Digital return (P1-11) Left exhaust temperature (P1-12) Right exhaust temperature
Illustration 4 g01444242
P2 ECM connector (P2-54) Digital return (P2-56) 8 V supply
Illustration 5 g01094844
Sensor connector (Pin A) Sensor supply (Pin B) Sensor return (Pin C) SignalTest Step 1. Check for "Active" or "Logged" Diagnostic Codes
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the Engine Control Switch (ECS) to the STOP position. Turn the main disconnect switch to the ON position.
Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes.Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Determine if a -8 diagnostic code is active for one of the exhaust temperature sensors.Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a terminal.Expected Result:No diagnostic code is active for the exhaust temperature sensors.Results:
OK - No diagnostic codes are active.Repair: If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct procedures for inspecting electrical connectors.STOP
Not OK - A -8 diagnostic code is active or the diagnostic code is logged several times. Proceed to Test Step 2.Test Step 2. Check the Digital Supply Voltage at the Sensor Connector
Turn the ECS to the OFF position. Turn the main disconnect switch to the OFF position.
Disconnect the suspect sensor(s) at the sensor connector.
Turn the ECS to the STOP position. Turn the main disconnect switch to the ON position.
Measure the voltage on the ECM side of the sensor connector between pin A and pin B for the suspect sensor(s).Expected Result:The supply voltage is 8.0 0.4 VDC.Results:
OK - The supply voltage is 8.0 0.4 VDC. Proceed to Test Step 4.
Not OK - The supply voltage is not 8.0 0.4 VDC. Proceed to Test Step 3.Test Step 3. Check the Digital Supply Voltage at the ECM
Turn the ECS to the OFF position. Turn the main disconnect switch to the OFF position.
Remove the supply wire from P1-4. Install a wire jumper into the socket for P1-4.
Remove the supply wire from P2-56. Install a wire jumper into the socket for P2-56.
Turn the ECS to the STOP position. Turn the main disconnect switch to the ON position.
Measure