Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P1668 : Generator L-Terminal Control CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Generator Turn On Signal | P1668 | P1668 | P1668 | -- |
Circuit/System Description
The engine control module (ECM) uses the generator turn ON signal circuit to control the load of the generator on the engine. A high side driver in the ECM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. The ECM monitors the state of the generator turn ON signal circuit. The ECM should detect low voltage on generator turn ON signal circuit when the ignition is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM should detect high voltage on the generator turn ON signal circuit. The ECM performs tests to determine the status of the generator turn ON signal circuit.
Conditions for Running the DTC
| • | No generator, crankshaft position (CKP) sensors, or camshaft position (CMP) sensor DTCs are set. |
| • | The ignition ON, engine OFF for the ignition on test. |
| • | The engine running for the run test. |
Conditions for Setting the DTC
| • | During the ignition ON test, the ECM detects high voltage on the generator turn on signal circuit for 5 seconds. |
| • | During the RUN test, the ECM detects low voltage on the generator turn on signal circuit for 15 seconds. |
Action Taken When the DTC Sets
| • | The instrument panel cluster (IPC) illuminates the charge indicator. |
| • | The driver information center (DIC) displays the CHARGING SYSTEM / GENERATOR FAULT warning message. |
Conditions for Clearing the DTC
DTC P1668 is a C type DTC.
Reference Information
Schematic Reference
Starting and Charging Schematics
Connector End View Reference
Electrical Information Reference
Circuit/System Testing
- Ignition OFF, disconnect the X1 harness connector at the generator.
- Ignition ON, test for less than 1 volt between the generator turn on signal circuit terminal 1 and ground.
- Engine running, test for greater than 3.5 volts between the signal circuit terminal 1 and ground.
- If the circuit tests normal, replace the generator.
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If less than the specified range, test the generator turn on signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
