FORK 9H7024 - Caterpillar

Illustration 1 g02551058
Connections of the Ambient Air Temperature SensorThe FMI 08 diagnostic code indicates that the electronic control module (ECM) has detected that signal frequency or signal pulse width or the period of the signal is abnormal.This code may mean that one of the following problems has occurred:
The sensor has failed.
There are intermittent connections.
There are poor connections.
There are loose mechanical devices.
The ECM has failed. The failure of the ECM is unlikely.
Electromagnetic interference is present.Test Step 1. CHECK THE CONTROL AND THE MACHINE HARNESS
Turn the disconnect switch and the key start switch to the ON position.
Disconnect the machine harness from the ambient air temperature sensor.
At the machine harness for the sensor, measure the voltage (DCV) between the signal contact 3 (wire C453-YL) and the negative battery contact 2 (wire J842-BK).Expected Result:The voltage is 8 0.5 DCV.Results:
OK - The voltage is 8 0.5 DCV.Repair: The ECM and the machine harness are correct. The sensor has failed. Replace the sensor.STOP
NOT OK - The voltage is greater than 8 0.5 DCV. The ECM or the machine harness has failed. Proceed to test step 2.Test Step 2. CHECK THE NEGATIVE BATTERY CIRCUIT OF THE MACHINE HARNESS
The sensor remains disconnected.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the J1 and J2 machine harness connectors from the ECM.
At the machine harness connector of the sensor, measure the resistance between the negative battery contact 2 (wire J842-BK) and connector contact J1-45 (wire J842-BK).Expected Result:The resistance is less than 5.0 ohms.Results:
OK - The resistance is less than 5.0 ohms. The machine harness is correct. Proceed to test step 3.
NOT OK - The resistance is greater than 5000 ohms. Repair: The machine harness has failed. The ground circuit in the machine harness is open. Repair the machine harness or replace the machine harness.STOPTest Step 3. CHECK FOR A SHORTED MACHINE HARNESS
The sensor and the ECM remain disconnected from the machine harness.
The disconnect switch and the key start switch remain in the OFF position.
At the machine harness connector for the sensor, measure the resistance between the signal contact 3 (wire C453-YL) and the supply contact 1 (wire K983-BU).Expected Result:The resistance is greater than 5000 ohms.Results:
OK - The resistance is greater than 5000 ohms. The harness circuit resistance is correct. Proceed to test step 4.
NOT OK - The resistance is less than 5000 ohms. Repair: The machine harness has failed. There is a short between the +battery circuit and the signal circuit in the machine harness. Repair the machine harness or replace the machine harness.STOPTest Step 4. CHECK FOR AN OPEN HARNESS
The sensor and the ECM remain disconnected from the machine harness.
The disconnect switch and the key start switch remain in the OFF position.
Measure the resistance of the signal circuit from the connector contact J2-25 (wire C453-YL) of the ECM to connector contact 3 (wire C453-YL) for the sensor.Expected Result:The resistance is less than 5.0 ohms.Results:
OK - The resistance is less than 5.0 ohms. The circuit resistance of the machine harness is correct.Repair: