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P0621




DTC P0621

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0621
- Generator L-Terminal Circuit

Diagnostic Fault Information






Circuit/System Description

The engine control module (ECM) uses the generator turn ON control circuit to control the load of the generator on the engine. A high side driver in the ECM applies a duty cycled voltage to the voltage regulator. The duty cycle controls the voltage regulator to turn the field circuit ON and OFF. The ECM monitors the state of the generator turn ON control circuit. The ECM should detect low voltage on the generator turn on control 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 when the duty cycle voltage is commanded high and a low voltage when the duty cycle voltage is commanded low. on the generator turn on control circuit.

Conditions for Running the DTC

* Ignition ON, engine OFF (Prior to Ignition ON, the ignition must have been OFF for at least 5 seconds)

* The engine is running for the run test

Conditions for Setting the DTC

* Ignition ON, engine OFF - The ECM detects greater than 3.5 V on the generator control circuit for 5 seconds.

* Engine running - The ECM detects a low voltage for 15 seconds on the generator control circuit when the duty cycle voltage is commanded high.

* Engine running - The ECM detects a high voltage for 15 seconds on the generator control circuit when the duty cycle voltage is commanded low.

* If the DTC(s) are not currently set, reference the freeze frame/failure records to determine if the ignition ON, engine OFF or Engine running test failed.

* Operate vehicle within the conditions defined in the records to verify the DTC does not reset.

Action Taken When the DTC Sets

DTC P0621 is a C type DTC.

Conditions for Clearing the DTC

* Ignition ON, engine OFF- Low voltage or no PWM signal detected.

* Engine running - A 5-90% duty cycle is detected.

Reference Information

Schematic Reference

Starting and Charging Schematics [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views Outside Rearview Mirror - Driver

Description and Operation

Charging System Description and Operation Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Testing

1. Verify a test lamp illuminates between the G13 Generator B+ circuit terminal A X2 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Remove the test lamp and disconnect the B+ cable at the G13 Generator.

2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Remove the test lamp, disconnect the battery negative cable, and disconnect the G13 Generator B+ cable.

2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If the test lamp illuminates

2. Disconnect the X1 harness connector at the G13 Generator, ignition ON.

3. Test for 3.0- 5.5 V between the control circuit terminal 1 and ground.

• If less than 3.0 V

1. Ignition OFF, disconnect the harness connectors at the K20 Engine Control Module.

2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the control circuit end to end.

• If greater the 2 ohms, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K20 Engine Control Module.

• If greater than 5.5 V

1. Ignition OFF, disconnect the harness connectors at the K20 Engine Control Module, Ignition ON.

2. Test for less than 1 V between the control circuit and ground.

• If greater than 1 V, repair the short to voltage on the circuit.

• If less than 1 V, replace the K20 Engine Control Module.

• If between 3.0-5.5 V

4. Test or replace the G13 Generator.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Generator Replacement (2.4L LEA) Service and RepairGenerator Replacement (2.0L LHU) Service and Repair

* Control Module References Control Module References for Engine Control Module replacement, programming, and setup

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