LENS AS 4877761 - Caterpillar

System OperationUse this procedure to troubleshoot any suspect problems with the following sensors for the primary ECM:
Intake manifold air temperature sensor
Illustration 1 g03352710
Typical primary schematic
Illustration 2 g03352711
Terminal locations at the P1 ECM connector for the passive sensor (P1-14) Inlet manifold air temperature (P1-3) Sensor return
Illustration 3 g01155187
Terminal locations at the connector for the passive analog sensors (Terminal 1) Sensor signal (Terminal 2) Sensor return
Table 2
Troubleshooting Test Steps    Values    Results    
1. Check for "Active" or "Logged" Diagnostic Codes
A. Connect Caterpillar Electronic Technician (ET) to the service tool connector.
B. Restore the electrical power to the ECM.
C. 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.
D. Determine if the problem is active and related to one of the following diagnostic codes:
-3
-4    
Codes    
Results: No diagnostic codes are active at this time.
Repair: The problem may be intermittent. If the problem is intermittent refer to Troubleshooting, "Electrical Connectors - Inspect"
Results: An active -3 diagnostic code is present.
Proceed to Test Step 2
Results: An active -4 diagnostic code is present.
Proceed to Test Step 4
   
2. Check for a Short to the +Battery at the Sensor Connector
A. Measure the voltage on the harness side of the sensor connector between pin 1 and pin 2 for the suspect sensor.
   
+Battery    
Results: The supply voltage is less than Battery voltage.
Proceed to Test Step 3
Results: The supply voltage is equal to Battery voltage.
Repair: There is a short in the harness to the +Battery. Repair the wiring.
Verify that the repair eliminated the problem.    
3. Create a Short at the Sensor Connector
A. Turn the main disconnect switch to the OFF position.
B. Disconnect the suspect sensor.
C. Use a wire jumper in order to create a short between terminal 1 (signal) and terminal 2 (sensor return) at the sensor connector.
D. Restore the electrical power to the ECM.
E. Access the "Active Diagnostic Code" screen on Cat ET.