DTC P0621 GAS
Diagnostic Instructions
DTC Descriptor
DTC P0621 : Generator L-Terminal Circuit
Diagnostic Fault Information
Circuit
| Short to Ground
| Open/High Resistance
| Short to Voltage
| Signal Performance
|
Generator Turn ON Signal
| P0621
| P0621
| P0621
| --
|
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 the Ignition ON and RUN 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 ignition on test. |
| • | The engine is 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 SERVICE BATTERY CHARGING SYSTEM warning message. |
Conditions for Clearing the DTC
DTC P0621 is a C type DTC.
Reference Information
Schematic Reference
Starting and Charging Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Charging System Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
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 less than 1 volt between the generator turn on signal circuit terminal B X1 and ground.
| ⇒ | If greater than the specified range, test the generator turn on signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
- Engine running, test for greater than 3.5 volts between the generator turn on signal circuit terminal B and ground.
| ⇒ | 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. |
- If the circuit tests normal, test or replace the generator.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
DTC P0621 DIESEL
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. |
| • | The engine is running. |
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.
Reference Information
Schematic Reference
Starting and Charging Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Charging System Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- Ignition OFF, test for B+ between the generator B+ output terminal (stud) to ground.
| ⇒ | If less than the specified range, test the circuit for a short to ground, an open or a high resistance. |
- Ignition OFF, disconnect the harness connector at the generator.
- Ignition ON, test for greater than 3.5 V 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.
