SWASHPLATE 9J7738 - Caterpillar

System Operation Description:This procedure checks the circuit for the diagnostic enable switch for proper operation. The Engine Control Module (ECM) does not provide diagnostics for the circuit for the diagnostic enable switch.Background Information for the Diagnostic Enable SwitchThe diagnostic enable switch prompts the check engine lamp to indicate the flash codes.A problem with the circuit for the diagnostic enable switch will cause the check engine lamp to operate incorrectly.There are two possible wiring configurations for the ECM to receive the status of the diagnostic enable switch:Hard Wired - In this configuration, the diagnostic enable switch is wired directly to terminal P1-46. The diagnostic enable switch is closed when the switch is depressed. This connects the ECM input to return. The "Diagnostic Enable Switch" parameter must be set to "J1/P1:46" in order to use this configuration.J1939 Data Link - In this configuration, the status of the diagnostic enable switch is sent from a J1939 device to the engine ECM via the J1939 data link. The "Diagnostic Enable Switch" parameter must be set to "J1939 - Body Controller", to "J1939 - Cab Controller", or to "J1939 - Instrument Cluster" in order to use this configuration.The following components can cause problems with the input from the diagnostic enable switch:
Electrical connector or wiring
Diagnostic enable switch
J1939 device
Engine ECMThe most likely cause of a problem is a problem with an electrical connector or wiring. The least likely cause is a problem with an ECM.Diagnostics on the Caterpillar Electronic Technician (ET)Wiggle Test - The wiggle test allows you to monitor the "Diagnostic Enable Switch" parameter while you wiggle the wiring. This helps to identify faulty electrical connections.For additional information regarding the wiggle test, refer to the documentation that accompanies your Cat ET software.
Illustration 1 g01163906
Schematic for the circuit for the diagnostic enable switch
In this configuration, the switch is wired directly to the ECM.
Note: The return wire may be connected to P1-3, to P1-5, or to P1-18.
Illustration 2 g01163912
Terminals on the P1 connector for the circuit for the diagnostic enable switch
(5) Return
(46) Diagnostic enable switch Test Step 1. Check the Configuration Parameters
Establish communication between Cat ET and the ECM. Refer to Troubleshooting, "Electronic Service Tools", if necessary.
Verify that the value of the "Diagnostic Enable Switch" parameter matches the configuration of the vehicle's wiring. Expected Result:The parameter is programmed correctly.Results:
The parameter is programmed correctly. - Proceed to Test Step 2.
The parameter is not programmed correctly. - Repair: Program the correct value for the parameter. Test the operation of the diagnostic enable switch. If the switch is operating correctly, the problem is resolved.If the diagnostic enable switch is not operating correctly and a J1939 device is used to send the status of the switch to the ECM, send the vehicle to an OEM dealer for repair.If the diagnostic enable switch is not operating correctly and the switch is wired directly to the ECM, proceed to Test Step 2.Test Step 2. Check for a Short Circuit
Inspect the seal around the signal wire and the return wire at the P1 connector. Verify