24H Motor Grader Transmission Electronic Control System And Hydraulic Calibrations Caterpillar

Illustration 1	g00514061
Schematic Of The Brake Pedal Position Sensor.

This fault is recorded when the ECM reads the signal from the brake pedal (wire G745-PK) and the ECM determines that the signal is shorted to + battery (FMI F03). The brake pedal position sensor is a PWM sensor. The signal wire of the brake pedal position sensor (wire G745-PK) connects to contact J2-5 of the ECM. The brake lamp does not work when this fault is active.

Service Notes: Ensure that the CID 0468 FMI 03 fault is on hold and that the fault present indicator is ON.

1. CHECK THE ECM AND HARNESS.

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

   2. Disconnect the machine harness from the sensor.

   3. At the machine harness connector for the sensor, measure the voltage (DCV) between signal contact A (wire 126-PK) and ground contact B (wire G939-PK).

      Expected Result: Voltage is at battery voltage.

      Results:

      • YES - Voltage is at battery voltage (24 DCV) harness is correct. Go to Step 3.

      • NO - Voltage is NOT at battery voltage. The harness is defective. Go to Step 2.

2. CHECK HARNESS GROUND CIRCUIT.

   1. The sensor remains disconnected.

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

   3. At the machine harness connector for the sensor, measure the resistance between ground contact B (wire G939-PK) and frame ground.

      Expected Result: Resistance is greater than 2.0 Ohms.

      Results:

      • YES - Resistance is greater than 2.0 Ohms. The ground circuit in the harness is defective. There is an open circuit between ground contact B (wire G939-PK) and frame ground. Repair the machine harness or replace the machine harness.

      • NO - Resistance is less than 2.0 Ohms. Harness resistance is correct. There is a problem in the +battery supply for the sensor. Correct the problem.

3. CHECK FOR OPEN HARNESS.

   1. The sensor and the ECM remain disconnected from the machine harness.

   2. The disconnect switch remains OFF.

   3. Check the continuity of the signal circuit from connector J2-5 to contact C (wire G745-PK) of the sensor harness connector.

      Expected Result: There is continuity.

      Results:

      • YES - There is continuity. The signal circuit is correct. Replace the sensor. If the problem is still present the ECM is defective. Replace the ECM. See Testing and Adjusting, "ECM - Replacement".

      • NO - There is NO continuity. The signal circuit is defective. The signal circuit is open in the machine harness. Repair the machine harness or replace the machine harness.