SEAL 5P5902 - Caterpillar

Illustration 1 g02025091
Ambient Air Temperature sensor schematic
This diagnostic code is for the Ambient Air Temperature sensor. An FMI 04 indicates the machine ECM has determined the sensor output signal voltage is below the normal limit. Possible causes for this diagnostic code are:
The sensor may have failed.
The sensor output signal circuit may be shorted to ground.
The machine ECM may have failed, but is unlikely.Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes now, but clear those codes after the original diagnostic code has been corrected. Note: Poor connections are often the cause of a problem in electrical circuits. Before performing this procedure, inspect all of the harness connectors involved in the circuit. Verify that all of the connections in the circuit are clean, secure, and in good condition. If a problem is found with any of the connections: correct the problem and verify that diagnostic code CID 0171 FMI 04 is still active, before performing the following procedures. System Response:This failure may cause the Ambient Air Temperature sensor to indicate a maximum temperature, either constantly, or intermittently. Test Step 1. CHECK THE SENSOR THE ECM, AND THE MACHINE HARNESS.
Turn the disconnect switch and the key start switch to the OFF position.
Disconnect the machine harness connector from the Ambient Air Temperature sensor.
Turn the key start switch and the disconnect switch to the ON position.
Observe the status of the diagnostic code. Expected Result:The CID 0171 FMI 04 code remains active. Results:
YES - The CID 0171 FMI 04 code remains active. The sensor is not the problem. Go to Test Step 2.
NO - The CID 0171 FMI 04 code is