PIN GP- 2841901 - Caterpillar

Illustration 1 g01043489
Schematic of the rear service brake and retarder pressure switch
This diagnostic code is associated with the rear service brake and retarder pressure switch. This diagnostic code is recorded when the Power Train/Chassis Electronic Control Module (ECM) reads the voltage of the switch as being below normal.The possible causes of this diagnostic code are listed:
The switch has failed.
(Wire K992-PU(Purple)) is shorted to frame ground between the switch and the ECM.
The ECM has failed. This is unlikely.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 1640 FMI 04 is active before performing this procedure.Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure.System Response:The ECM will use the switch to determine the appropriate shift points. If the switch operates properly, the machine will operate correctly.Test Step 1. CHECK THE SWITCH
Turn the battery disconnect switch and the key start switch to the ON position.
Ensure that the diagnostic code is active.
Access the Caterpillar Electronic Technician (ET). View the display that is shown for the switch. For more information about the ET, see Systems Operation, Troubleshooting, Testing and Adjusting, "Service Tools".
Activate the switch. De-activate the switch. Expected Result:The diagnostic code changes from being active to being not active as the switch is cycled.Results:
OK - The diagnostic code is active. Then, the diagnostic code is not active as the switch is cycled. The switch has failed.Repair: Repeat this test "CHECK THE SWITCH" in order to verify that the switch has failed. Replace the switch.STOP
NOT OK - The diagnostic code remains active. The diagnostic code does not change. The machine harness has failed or the ECM has failed. Proceed to Test Step 2.Test Step 2. CHECK FOR A SHORT TO GROUND
Turn the key start switch and the battery disconnect switch to the OFF position.
Remove all jumper wires that were previously installed.
Disconnect the J1 and J2 machine harness connectors from the ECM.
At the J1 machine harness connector for the ECM, measure the resistance from the signal contact J1-22 (wire K992-PU(Purple)) to all possible sources of frame ground. Expected Result:The resistance for each measurement should be greater than 5 ohms.Results:
OK - Each resistance measurement is greater than 5 ohms. The harness is correct. The ECM may have failed. Proceed to Test Step 3.
NOT OK - Each resistance measurement is less than 5 ohms. The machine harness has failed.Repair: There is a short in the machine harness. The short is between the signal (wire K992-PU(Purple)) and the wire with the low resistance measurement. Repair the machine harness or replace the machine harness.STOPTest Step 3. CHECK IF THE DIAGNOSTIC CODE REMAINS
Inspect the contacts of the harness connectors and clean the harness connectors.
Reconnect all the harness connectors.
Turn the battery disconnect switch and the key start switch to the ON position.
Operate the machine.
Check the status of the CID 1640 FMI 04. Expected Result: