P1637

Schematic:

CIRCUIT DESCRIPTION
The L-terminal circuit from the generator is a discrete circuit (a discrete circuit has no splices and only one source and one destination) into the PCM. The PCM applies ignition voltage to the generator L terminal circuit. A small amount of current flows from this circuit through the generator windings to create a magnetic field which starts the generator process. When the generator is at operating speed and producing voltage, a solid state switch for the L terminal circuit in the generator opens and the PCM detects that the initial startup current flow has stopped.

The PCM expects to detect low voltage on the L terminal circuit prior to the generator rotating at operating speed and conversely expects the circuit to be at ignition voltage potential when the generator is operational. When the PCM detects a fault (circuit shorted to ground, or circuit shorted to a voltage), this DTC will set.

CONDITIONS FOR RUNNING THE DTC
Engine operating.

CONDITIONS FOR SETTING THE DTC
The PCM detects an improper voltage on the generator L terminal circuit.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM stores the DTC information into memory when the diagnostic runs and fails.
^ The Malfunction Indicator Lamp (MIL) will not illuminate.
^ The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ A History DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
^ A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.
^ Use a scan tool in order to clear the MIL/DTC.

DIAGNOSTIC AIDS

IMPORTANT:
^ Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
^ For any test that requires probing the PCM or component harness connectors, use the J 35616-A connector test adapter kit. Using this kit prevents damage to the harness connector terminals. Refer to Using Connector Test Adapters in Diagrams.

A generator fault, such as a shorted output diode, malfunctioning regulator, open or shorted rotor, or open sense lead may cause a low battery charge. Refer to A Diagnostic Starting Point - Engine Electrical in Starting and Charging for further information and generator diagnosis. Testing and Inspection

Use a scan tool in order to diagnosis the generator circuits. A scan tool displays Generator L-Terminal Inactive when there is a concern with the L-terminal circuit.

For an intermittent condition, refer to Symptoms. Symptom Related Diagnostic Procedures

TEST DESCRIPTION

Steps 1 - 10:

Steps 11 - 14:

The numbers below refer to the step numbers on the Diagnostic Table.
2. This step determines if a fault is present.
12. A poor connection at the generator causes no output.