DOOR AS 6T7231 - Caterpillar

System OperationUse this procedure to troubleshoot any suspect problems with the following sensors:
Inlet manifold temperature sensor
Engine oil temperature sensorThe sensor signal for the passive sensors is routed from the ECM to the connector for the right rail. The sensor signal is then routed to terminal 1 of each sensor connector. The sensor return for the passive sensors is routed from the ECM to the connector for the right rail. The sensor return is then routed to terminal 2 of each sensor connector.
Illustration 1 g01242605
Typical schematic
Illustration 2 g01242612
P1 ECM connector
(P1-3) Sensor return (left rail)
(P1-14) "Inlet manifold temperature sensor"
(P1-26) Engine oil temperature sensor
(P1-35) Sensor return (right rail)
Illustration 3 g01163206
Sensor connector
(Terminal 1) Sensor signal
(Terminal 2) Sensor return
Illustration 4 g01234146
Location of ECM connectors
Test Step 1. Check for "Active" or "Logged" Diagnostic Codes
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Restore power to the ECM.
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 the problem is active and related to one of the following diagnostic codes:
3
4Expected Result:No diagnostic codes are active at this time.Results:
OK - No diagnostic codes are active at this time.Repair: The problem may be intermittent. If the problem is intermittent refer to Troubleshooting, "Inspecting Electrical Connectors".STOP
Not OK - An active 3 diagnostic code is present. Proceed to Test Step 2.
Not OK - An active 4 diagnostic code is present. Proceed to Test Step 4.Test Step 2. Check for Battery Voltage on the Signal Wire
Measure the voltage on the harness side of the sensor connector between pin 1 and engine ground for the suspect sensor(s). Expected Result:The signal voltage is less than Battery voltage.Results:
OK - The signal voltage is less than Battery voltage. Proceed to Test Step 3.
Not OK - The signal voltage is equal to Battery voltage.Repair: There is a short in the harness to the Battery. Repair the wiring.STOPTest Step 3. Create a Short at the Sensor Connector
Disconnect the suspect sensor.
Use a wire jumper in order to create a short between terminal 1 (signal) and terminal 2 (sensor return) at the sensor connector.
Restore power to the ECM.
Access the "Active Diagnostic Code" screen on Cat ET. Check for an active 4 diagnostic code for the suspect sensor. Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Remove power from the ECM. Expected Result:A 4 diagnostic code is now active for the suspect sensor(s).Results:
OK - A 3 diagnostic code was active before creating the short at the sensor connector. A 4 diagnostic code became active after creating the short at the sensor connector.Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.STOP
Not OK - A 3 diagnostic code is still active for the suspect sensor(s). Proceed to Test Step