CORE AS- 2153589 - Caterpillar

Illustration 1 g01994554
Schematic of the Ambient Air Temperature Sensor
Sales models 854K/992K
This diagnostic code is associated with the ambient air temperature sensor. This diagnostic code is recorded when the ECM reads the signal from the sensor (wire C453-YL(Yellow)) as being shorted to ground. The sensor produces a PWM signal. The sensor signal wire (C453-YL(Yellow)) connects to contact J1-12 of the ECM.The possible causes of this diagnostic code are listed:
The signal circuit (wire C453-YL(Yellow)) is shorted to ground.
The sensor has failed.
The ECM has failed. This is unlikely.Note: The test step “CHECK THE SENSOR” can create numerous related diagnostic codes. The related diagnostic codes will be shown as being not active, after all of the harnesses have been reconnected. Clear all related diagnostic codes after this procedure is completed.Test Step 1. CHECK THE SENSOR.
Turn the disconnect switch and the key start switch to the ON position.
Ensure that the diagnostic code is active.
Observe the status of the diagnostic code. Then, disconnect the sensor from the machine harness. Expected Result:The diagnostic code remains active. When the sensor is unplugged the diagnostic changes to an FMI 03.Results:
OK - The diagnostic code is no longer active. The machine harness and the ECM are operating properly. Proceed to test step 2.
NOT OK - The diagnostic code remains active. The sensor has not failed. The machine harness may have failed or the ECM may have failed. Proceed to Test Step 2.Test Step 2. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND.
The sensor remains disconnected from the machine harness.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the J2 machine harness connector from the ECM.
At the J2 machine harness connector, measure the resistance from contact J1-12 (wire C453-YL(Yellow)) to ground. Expected Result:The resistance is greater than 5000 ohms.Results:
OK - The resistance is greater than 5000 ohms.Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Testing and Adjusting, "Module - Replace".STOP
NOT OK - The resistance is less than 5000 ohms.Repair: The machine harness has failed. There is a short in the machine harness between the signal circuit and ground. Repair the machine harness or replace the machine harness.STOP