CAB GP-BASIC 3157319 - Caterpillar

Illustration 1 g02570176
Connections of the Downshift Switch
This diagnostic code is associated with the Transmission Downshift Switch. The Transmission Downshift Switch is connected to two inputs of the ECM. One contact is open and the other contact is grounded during proper operation. This FMI 04 means that the ECM has determined that both circuits are grounded.Possible causes of this diagnostic code are listed:
A switch signal is shorted to ground.
A switch has failed.
The ECM has failed. This situation 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.Note: 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 0621 FMI 04 is active before performing this procedure.Note: Use a digital multimeter for the measurements in this procedure.
Table 1
Downshift Switch
Switch Position G762-BR(Brown) Circuit
N/O J1-43 G761-YL(Yellow) Circuit
N/C J1-42
Depressed Closed Open
Released Open Closed System Response:Transmission downshifts are disabled.Test Step 1. CHECK THE OPERATION OF THE SWITCH IN THE RELEASED POSITION
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness connector from the switch harness assembly.
Connect one lead from a multimeter to contact 2 (wire 202-BK(Black)) of the switch harness assembly.
Connect the other lead from a multimeter to contact 7 (wire G761-YL(Yellow)) of the switch harness assembly.
Measure the resistance between contact 2 and contact 7. Note the resistance.
Disconnect the lead from contact 7 and connect the lead to contact 8 (wire G762-BR(Brown)).
Measure the resistance between contact 2 and contact 8. Note the resistance. Expected Result:The resistance from contact 2 to