• | 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. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Generator Turn On Signal | P0621 | -- | P0621 | -- |
The engine control module (ECM) uses the generator turn ON signal circuit, or L-terminal 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 ignition is ON. |
• | The system voltage is between 9.5-18 volts. |
The ECM detects high or low voltage on the generator turn on signal circuit for 15 seconds.
• | The ECM will command the charge indicator ON and warning message to be displayed on the driver information center (DIC), if equipped. |
• | The ECM will not illuminate the malfunction indicator lamp (MIL). |
• | The ECM will store conditions, which were present when the DTC set as Fail Records data only. |
• | The DTC will pass when the conditions for setting the DTC are no longer met. |
• | A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
Starting and Charging Schematics
Charging System Description and Operation
Control Module References for scan tool information
⇒ | 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 signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for ECM replacement, setup, and programming. |