5130, 5130B and 5230 Excavators, 784B, 785B, 785C, 789B, 789C, 793B and 793C Off-Highway Truck/Tractors and 992G, 994 and 994D Wheel Loaders Vital Information Management System (VIMS) Caterpillar

Illustration 1	g00730066
Schematic of the Ambient Air Temperature Sensor

This diagnostic code is recorded when the VIMS reads the voltage of the ambient air temperature sensor and the voltage is above normal. The sensor sends a PWM signal to the VIMS module.

The possible causes of this diagnostic code are listed here:

• A shorted harness

• An open supply circuit to the sensor

• A failed sensor

• An open circuit

• The VIMS interface module may have failed. This is unlikely.

Note: Ensure that the diagnostic code is still active.

Note: The following procedure can create numerous related diagnostic codes. Reconnect all harnesses. Then, the related diagnostic codes will be shown as being NOT active. Complete the following procedure. Then, clear all of the related diagnostic codes.

1. CHECK THE SUPPLY VOLTAGE AT THE SENSOR.

   1. Turn the disconnect switch and the key start switch to the ON position.

   2. Check the voltage at the machine harness connector of the sensor from contact A (sensor supply) to contact B (ground). Do NOT disconnect the sensor. Use the 7X-1710 Cable probes to measure the voltage.

      Expected Results: The voltage should measure approximately 8 DCV.

      Results:

      • OK - Voltage is approximately 8 DCV. The voltage is correct. Proceed to 3.

      • NOT OK - Voltage is not approximately 8 DCV. There is an open in the machine harness or the ECM has failed. It is unlikely that the ECM has failed. Proceed to 2.

2. CHECK FOR AN OPEN IN THE SUPPLY CIRCUIT.

   1. The key start switch and the disconnect switch remain in the ON position.

   2. Disconnect the sensor from the machine harness.

   3. At the machine harness connector for the sensor, measure the voltage from contact A (sensor supply) to frame ground.

      Expected Results: The voltage should measure approximately 8 DCV.

      Results:

      • OK - Voltage measures approximately 8 DCV. The return circuit is open. Repair the machine harness or replace the machine harness. STOP.

      • NOT OK - Voltage does not measure approximately 8 DCV. The supply circuit is open. Repair the machine harness or replace the machine harness. STOP.

3. CHECK THE SIGNAL CIRCUIT.

   1. Turn the disconnect switch and the key start switch to the ON position.

   2. Disconnect the machine harness connector from the sensor.

   3. At the machine harness connector for the sensor, measure the voltage between contact C (signal) and contact B (ground).

      Expected Results: The voltage should measure approximately 5 DCV.

      • OK - Voltage is approximately 5 DCV. The voltage is correct. Replace the sensor. STOP

      • NOT OK - Voltage is NOT approximately 5 DCV. The voltage is NOT correct. Proceed to 4.

4. CHECK FOR AN OPEN SIGNAL CIRCUIT.

   1. Turn the key start switch and the disconnect switch to the OFF position.

   2. The sensor remains disconnected from the machine harness.

   3. Disconnect the machine harness from the interface module.

   4. Place a jumper wire between contact C (signal) and contact B (ground) of the machine harness connector for the sensor.

   5. At the machine harness connector of the interface module, measure the resistance between the signal contact and frame ground.

      Expected Result: The resistance measures less than 10 ohms.

      Results:

      • OK - Resistance measures less than 10 ohms. The circuit is correct. Proceed to 5.

      • NOT OK - Resistance is greater than 5000 ohm. The circuit is open. Repair the machine harness or replace the machine harness. STOP.

5. CHECK THE SIGNAL WIRE FOR SHORTS.

   1. The disconnect switch and the key start switch remain in the OFF position.

   2. The machine harness remains disconnected from the VIMS interface module.

   3. Remove the jumper wire from contact C and contact B on the machine harness connector for the sensor.

   4. At the machine harness connector for the VIMS interface module, measure the resistance from the signal contact to all possible sources of +Battery.

      Expected Results: Each measurement is greater than 5000 ohms.

      • OK - Resistance measurements are greater than 5000 ohms. The ECM has failed. Refer to the Testing and Adjusting, "Module - Replace" section. STOP.

      • NOT OK - Resistance measured less than 5000 ohms. There is a short in the machine harness. Repair the machine harness or replace the machine harness. STOP.