ELEVATOR SPEED REDUCER GROUP 8J3923 - Caterpillar

Illustration 1 g00502958
Parking Brake Oil Pressure Switch SchematicThis switch has two inputs to the power train electronic control module (ECM). The inputs are normally open (N/O) and normally closed (N/C). CID 0070 FMI 04 service code is recorded when the status of both the N/O and N/C inputs of the switch are grounded.Note: Ensure that the desired fault CID 0070 FMI 04 is active.Note: The following procedure can create other faults that the power train ECM will detect. Ignore these created faults and clear the faults when this fault is corrected.
Table 1
Parking Brake Pressure Switch Status    
Parking Brake Pressure Switch    Terminal B
(N/O)
Wire 419-YL
J1-36    Terminal C
(N/C)
G764-PK
J1-27    
Low Pressure
Brake Engaged     Open     Closed    
High Pressure
Brake Engaged     Closed     Open    
Check for an open circuit.
Ensure that the fault is active.
Observe the ON/OFF status of the fault.
Disconnect the connector of the switch from the machine harness.Expected Result: The active fault changes from "04" to "03".Results:
YES - The switch or the switch's harness is failed. Repeat this test "Check for an open circuit" to verify the switch failure. Repair or replace the switch and or the switch's harness.
NO - The fault present indicator remains ON. The switch is not the cause of this fault. Proceed to Step 2.
Check the harness circuit.This test "Check the harness circuit" checks the continuity of the entire harness circuit that is faulty. The switch which was previously checked in test "Check for an open circuit" is included in this test.
Turn the disconnect switch to the OFF position.
Connect the switch connector to the machine harness.
Disconnect the machine harness from the power train ECM.
At the machine harness connector for the power train ECM, check the continuity to ground of the N/C contact and the N/O contact with the switch activated and not activated. See Table 1 "Parking Brake Pressure Switch Status".Expected Result: The continuity check does not agree with the table.Results:
YES - The continuity check does NOT agree with table. The harness circuit is faulty. There is a short to ground in the machine harness between the power train ECM and the switch. Repair the machine harness or replace the machine harness. STOP.
NO - The continuity check agrees with the table. The harness circuit is correct. It is unlikely that the power train ECM is faulty. Exit this procedure and perform CID 0070 FMI 04 again. If the cause is not found, replace the power train ECM. Refer to Testing and Adjusting, "Electronic Control Module (Power Train) - Replace" for information on replacing the power train ECM. STOP.