Diagnostic Instructions
Perform the
Diagnostic System Check - Engine Electrical prior to using this diagnostic procedure.
DTC Descriptor
DTC P0621: Generator L-Terminal Circuit
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
Control
| P0621
| --
| P0621
| --
|
Circuit/System Description
The engine control module (ECM) or powertrain control module (PCM) uses the charge indicator control circuit, or L-terminal circuit, to control the generator output, and the load of the generator on the engine. A high side driver in the ECM/PCM
applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. The generators internal regulator monitors the generator operation. If the regulator detects an internal failure, it will apply ground to the
charge indicator control circuit. The ECM/PCM monitors the state of the charge indicator control circuit, and turns the charge indicator ON if the circuit is shorted to ground or voltage.
Conditions for Running the DTC
| • | No crankshaft or camshaft position sensor DTCs are set. |
Conditions for Setting the DTC
The charge indicator control circuit is shorted to ground or shorted to voltage.
Action Taken When the DTC Sets
| • | The charge indicator turns ON. |
| • | The driver information center (DIC) displays the BATTERY NOT CHARGING message. |
Conditions for Clearing the DTC
| • | The DTC will pass when the condition for setting the DTC is no longer present. |
| • | A history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The charge indicator and DIC message will remain ON until the DTC passes or is cleared, even if the ignition is cycled. |
Reference Information
Schematic Reference
Starting and Charging Schematics
Connector End View Reference
Engine Electrical Connector End Views
Description and Operation
Charging System Description and Operation
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing - Single Generator (w/o K65)
- Ignition OFF, disconnect the harness connector at the generator.
- Ignition OFF, test for less than 1 V between the control circuit terminal B and ground.
| ⇒ | If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM/PCM. |
- Engine running, test for greater than 3.5 V between the control circuit terminal B and ground.
| ⇒ | If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM/PCM. |
- If the circuit tests normal, test or replace the generator.
Circuit/System Testing - Dual Generators (K65)
- Ignition OFF, disconnect the harness connector at the left generator.
- Ignition OFF, test for less than 1 V between the control circuit terminal B and ground.
| ⇒ | If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
- Engine running, test for greater than 3.5 V between the control circuit terminal B and ground.
| ⇒ | If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
- Engine running, left generator harness disconnected, verify that DTC P0621 sets.
| ⇒ | If DTC P0621 does not set, test or replace the left generator. |
- Ignition OFF, disconnect the harness connector at the right generator.
- Ignition OFF, test for less than 1 V between the signal circuit terminal B and ground.
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
- Engine running, test for greater than 3.5 V between the signal circuit terminal B and ground.
| ⇒ | 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. |
- If all circuits test normal, test or replace the right generator.
Repair Instructions
Operate the vehicle in order to verify the repair after completing the diagnostic procedure.
