DIFFERENTIAL & BEVEL GEAR GP 1477380 - Caterpillar

Illustration 1 g01945341
Connections of the increment/decrement switch for PTO 1
This diagnostic code is associated with the increment/decrement switch for PTO 1. The FMI 04 is recorded when the ECU determines that the voltage is below normal for the circuit. The switch has two inputs to the ECU. Only one input is grounded at any one time. When the switch is in the center position, neither input is grounded. When a circuit is measured with a voltmeter, an open circuit will measure approximately 8 VDC to ground and a closed circuit will measure approximately 0 VDC to ground. The possible causes of this diagnostic code are listed:
Contact "A" (wire Y974-BU(Blue)) is shorted to ground while contact "C" (wire Y975-BU(Blue)) is shorted to ground.
The switch has failed.
The ECU has failed. This is unlikely. Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all of the connections in the circuit are clean and secure. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 3395 FMI 04 is active before performing this procedure.
Table 1
Status of the Switch
MODE Switch Position J2-37
Y974-BU(Blue) Circuit J2-38
Y975-BU(Blue) Circuit
Increment Up Open Closed
Static Center Open Open
Decrement Down Closed Open Test Step 1. CHECK THE SWITCH.
Disconnect the switch from the machine harness.
Connect the multimeter in order to check for continuity between contact A (wire Y974-BU(Blue)) and contact B (wire J765-BU(Blue)) of the switch.
Actuate the switch in all three of the positions. Check for continuity in each position.
Connect the multimeter in order to check for continuity between contact B (wire J765-BU(Blue)) and contact C (wire Y975-BU(Blue)) of the switch.
Actuate the switch to all three of the positions. Check for continuity in each position. Expected Result:The continuity check agrees with Table 1.Results:
OK - The continuity check agrees. Proceed to Test Step 2.
NOT OK - The continuity check does not agree. The switch has failed.Repair: Replace the switch. Verify that the new switch corrects the diagnostic code.STOPTest Step 2. CHECK THE SIGNAL CIRCUITS IN THE HARNESS FOR A SHORT.
Reconnect the switch to the machine harness.
Disconnect the J1 and J2 machine harness connectors from the ECU.
At the machine harness connector for the ECU, check for continuity between contact J2-37 (wire Y974-BU(Blue)) and contact J2-63 (wire J765-BU(Blue)).
Press the switch. Release the switch and check for continuity.
At the machine harness connector for the ECU, check for continuity between contact J2-38 (wire Y975-BU(Blue)) and contact J2-63 (wire J765-BU(Blue)).
Press the switch. Release the switch and check for continuity. Expected Result:The continuity check agrees with Table 1.Results:
OK - The continuity check agrees.Repair: Reconnect the machine harness connectors. Verify that the diagnostic code has been corrected. If the cause of the problem is