For a complete wiring diagram Refer to Section 8W.When Monitored:With the ignition on. Engine running.Set Condition:When the PCM tries to regulate the generator field with no result during monitoring. One Trip Fault. Three good trips to turn off the MIL.Possible Causes(K125) GEN FIELD CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE(K125) GEN FIELD CONTROL CIRCUIT OPEN(K125) GEN FIELD CONTROL CIRCUIT SHORTED TO GROUNDGENERATORPCMAlways perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).1. ACTIVE DTCIgnition on, engine not running.With a scan tool, select View DTCs.Is the DTC Active at this time?YesGo To 2NoRefer to the INTERMITTENT CONDITION Diagnostic Procedure.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)2. GENERATOR OPERATION

Turn the ignition off.Disconnect the Generator Field harness connector.Using a 12-volt test light connected to ground, probe the (K125) Generator Field Control circuit in the Generator Field harness connector.Ignition on, engine not running.The DTC needs to be cleared before actuating the Generator Field, if the DTC is not cleared, the Generator Field may not be allowed to actuate.With the scan tool, actuate the Generator Field Control circuit.Does the test light illuminate brightly and flash on and off?YesReplace the Generator.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 33. (K125) GEN FIELD CIRCUIT SHORTED BATTERY VOLTAGE

Turn the ignition off.Disconnect the C2 PCM harness connector.Ignition on, engine not running.Measure the voltage on the (K125) Gen Field Control circuit in the Generator Field harness connector.Is the voltage above 0 volts?YesRepair the short to battery voltage in the (K125) Gen Field Control circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) NoGo To 44. (K125) GEN FIELD CIRCUIT OPEN

Turn the ignition off.Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.Measure the resistance of the (K125) Gen Field Control circuit from the Generator Field harness connector to appropriate terminal of the special tool #8815.Is the resistance below 5.0 ohms?YesGo To 5NoRepair the open in the (K125) Gen Field Control circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)5. (K125) GEN FIELD CIRCUIT SHORTED TO GROUND

Measure the resistance between ground and the (K125) Gen Field Control circuit in the Generator Field harness connector.Is the resistance below 100 ohms?YesRepair the short to ground in the (K125) Gen Field Control circuit.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 66. PCMBefore continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.Were there any problems found?YesRepair as necessary.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoReplace and program the Powertrain Control Module per Service Information.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)