Diagnostic Instructions
DTC Descriptor
DTC P0621 : Charge Indicator Control Circuit
Circuit/System Description
The ECM monitors the state of the charge indicator control circuit. The ECM should detect a low circuit voltage when the key is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM should detect a high circuit
voltage. The ECM performs key ON and RUN tests to determine the status of the charge indicator control circuit.
During the key ON test, if the ECM detects a high circuit voltage, DTC P0621 will set. DTC P0621 will also set if, during the RUN test, the ECM detects a low circuit voltage. When the DTC sets, the IPC will illuminate the charge indicator or a warning
message will be displayed in the driver information center (DIC) if equipped.
Conditions for Running the DTC
Key ON Test
| • | No generator, crankshaft position (CKP) sensors, or camshaft position (CMP) sensor DTCs are set. |
| • | The ignition is in RUN position. |
| • | The engine is not running. |
RUN Test
| • | No generator, CKP sensors, CMP sensor DTCs are set. |
Conditions for Setting the DTC
During the key ON test, the ECM detects high voltage on the charge indicator control circuit for at least 5 seconds. OR during the RUN test the ECM detects low voltage on the charge indicator control circuit for at least 15 seconds.
Action Taken When the DTC Sets
DTC P0621 is a C type DTC.
Conditions for Clearing the DTC
DTC P0621 is a C type DTC.
Diagnostic Aids
On vehicles equipped with a sense circuit connected to the voltage regulator. This circuit must have voltage for the charging system to operate properly. This circuit is used as a reference to control system voltage. All circuits must be tested at the
generator before replacing any components. refer to system schematic to confirm if the vehicle being serviced uses the sense circuit as part of the charging system.
Reference Information
Schematic Reference
Starting and Charging Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the generator.
- Ignition ON, test for B+ between the Ignition voltage circuit terminal D and ground.
| ⇒ | If less than the specified range, test the circuit for a short to ground, an open or a high resistance. |
- Ignition ON, test for greater than 3.5 volts between the charge indicator control circuit terminal B and ground.
| ⇒ | If less than the specified range, test the circuit for a short to ground, an open or a high resistance. If the circuit tests normal, replace the ECM. |
- If the circuit test normal, replace the generator.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
