STRIP 1M7838 - Caterpillar

Illustration 1 g02358017
Schematic for the parking brake switch
This diagnostic code is associated with the parking brake switch. This diagnostic code is recorded when the ECM reads the signal from the switch and the ECM determines that the signal is erratic, intermittent, or incorrect.The possible causes of this diagnostic code are listed:
An open circuit exists.
The ECM has failed. The ECM failing is unlikely.Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 0070 FMI 02 is active before performing this procedure.Note: Use a digital multimeter for the measurements in this procedure.Test Step 1. CHECK THE OPERATION OF THE SWITCH
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness connector or the wires from the switch.
Connect one lead from the multimeter to the common contact (2) for the switch.
Connect the other lead from the multimeter to the normally open contact (3) for the switch.
Measure the resistance between contact 2 and contact 3. Note the resistance.
Disconnect the lead from contact 3 and connect the lead to the normally closed contact (4).
Measure the resistance between contact 2 and contact 4. Note the resistance.
Disconnect the lead from contact 4 and connect the lead to the normally closed contact (1).
Measure the resistance between contact 2 and contact 1. Note the resistance. Expected Result:The resistance from contact 2 to contact 3 is greater than 5000 ohms, and the resistance from contact 2 to contact 3 is less than 5 ohms.Results:
YES - The resistance from contact 2 to contact 3and contact 2 to contact 4 is greater than 5000 ohms, and the resistance from contact 2 to contact 4 is less than 5 ohms. Proceed to Test Step 2.
NO - The resistance measurements do not differ. The switch has failed.Repair: Replace the switch.STOPTest Step 2. CHECK THE GROUND CIRCUIT OF THE SWITCH IN THE WIRE HARNESS.
Connect one lead from the multimeter to contact 2 of the wire harness connector for the switch.
Connect the other lead from the multimeter to frame ground.
Measure the resistance between contact 2 and frame ground. Expected Result:The resistance is less than 5 ohms.Results:
OK - The resistance is less than 5 ohms. The circuit is correct. Proceed to Test Step 3.
NOT OK - The resistance is greater than 5000 ohms. The circuit is open. The machine harness has failed.Repair: Repair the machine harness or replace the machine harness.STOPTest Step 3. CHECK THE SWITCH CIRCUITS FOR A SHORT CIRCUIT.
The disconnect switch and the key start switch remain in the OFF position.
Disconnect the machine harness connector from the ECM.
The connector for the switch remains disconnected.
At the machine harness connector for the ECM, measure the resistance from contacts J2-31 to contact (4), J2-28 to contact (3) and J2-29 to contact (1) . Expected Result:Each resistance measurement is greater than 5000 ohms.Results:
OK - Each resistance measurement is greater than 5000 ohms. The harness is correct. Proceed to