SLUG 7S2787 - Caterpillar

Illustration 4 g01251713
Terminal locations at the P1 ECM connector for the engine temperature sensors (P1-18) Sensor return #1 (P1-26) Ambient air temperature sensor
Illustration 5 g01155187
Terminal locations at the sensor connector for the engine temperature sensors (Terminal 1) Sensor signal (Terminal 2) Sensor return
Perform a 45 N (10 lb) pull test on each of the wires in the sensor connector and the ECM connector that are associated with the active diagnostic code.
Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasions and for pinch points from each of the temperature sensors to the ECM connector.Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The connectors and wiring appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem in the connectors and/or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.STOPTest Step 2. Check for Active Diagnostic Codes
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the keyswitch to the ON position.
Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Look for a 03 diagnostic code or a 04 diagnostic code.
Turn the keyswitch to the OFF position.Expected Result:No diagnostic codes are active.Results:
OK - No diagnostic codes are active.Repair: There is not an electrical problem with the temperature sensors at this time. The problem may have been related to a faulty connection in the harness. Carefully reinspect the connectors and wiring. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for additional information.STOP
Not OK - A 04 diagnostic code is active at this time. The ECM is detecting a short circuit for one of the temperature sensors. Proceed to Test Step 3.
Not OK - A 03 diagnostic code is active at this time. The ECM is detecting an open circuit for one of the temperature sensors. Proceed to Test Step 4.Test Step 3. Disconnect the Suspect Sensor in Order to Create an Open Circuit
Disconnect the suspect sensor from the engine harness.
Turn the keyswitch to the ON position.
Access the "Active Diagnostic Codes" screen on Cat ET and check for an active 03 diagnostic code for the suspect sensor.Note: Wait at least 30 seconds for activation of the diagnostic codes.
Turn the keyswitch to the OFF position.Expected Result:A 03 diagnostic code is now active for the suspect sensor.Results:
OK - A 04 diagnostic code was active before disconnecting the sensor. A 03 diagnostic code became active after the sensor was disconnected.Repair: There may be a problem with the sensor. Temporarily connect a new sensor to the