DTC Descriptor
DTC P0621 : Generator L- Terminal Circuit
Diagnostic Fault Information
Important: Always perform the
Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit/System Description
The powertrain control module (PCM) uses the generator turn on signal circuit to control the load of the generator on the engine. A high side driver in the PCM applies a voltage to the voltage regulator. When the PCM turns ON the high side driver, the
voltage regulator turns ON the field circuit. When the PCM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.
The PCM monitors the state of the generator turn on signal circuit. With the engine running, the PCM should detect a high generator turn on signal circuit, or when the charging system malfunctions. If the PCM detects a low generator turn on signal circuit,
DTC P0621 will set.
Conditions for Running the DTC
Key ON Test
| • | The ignition is in RUN position. |
| • | The engine is not running. |
RUN Test
| • | The engine speed is less than 3,00 RPM. |
Conditions for Setting the DTC
| • | During the key ON test, the PCM detects high voltage on the generator turn on signal circuit for at least 5 seconds. |
| • | During the RUN test the PCM detects low voltage on the generator turn on signal circuit for at least 15 seconds. |
Action Taken When the DTC Sets
| • | The PCM will command the charge indicator and or warning message to be illuminated on the instrument panel cluster (IPC) and the driver information center (DIC), if equipped. |
| • | The PCM will not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM will store conditions, which were present when the DTC set as Fail Records data only. |
Conditions for Clearing the DTC
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | Using the scan tool Clear DTC Information function can clear the DTC. |
Reference Information
Schematic Reference
Starting and Charging Schematics
Connector End View Reference
Engine Electrical Connector End Views
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- With ignition ON, and the engine OFF.
- Disconnect the generator harness and measure the voltage of the generator turn on signal circuit, should read near 0 volts.
| ⇒ | If greater than 0 volts test the generator turn on signal circuit for a short to voltage, or replace the PCM. |
- With ignition ON, and the engine running, the voltage of the generator turn on signal circuit, should read near 5 volts.
| ⇒ | If no voltage is measured, test the generator turn on signal circuit for a short to ground, an open or a high resistance or replace the PCM. |
- Go to
Charging System Test.
Repair Instructions
Important: Always perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for PCM replacement, setup, and programming.
