For 1990-2009 cars

### Diagnostic Instructions

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

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

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P0622: Generator F-Terminal Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
B+ | P0622 | P0622 | -- | --
Generator Field Duty Cycle Signal | P0622 | P0622 | P0622 | P0622

### Circuit/System Description

The engine control module (ECM) uses the generator field duty cycle signal circuit to monitor the duty cycle of the generator. The generator field duty cycle signal circuit connects to high side of the field windings in the generator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field windings ON and OFF. The ECM uses the PWM signal input to determine the generator load on the engine. This allows the ECM to adjust the idle speed to compensate for high electrical loads. The ECM monitors the status of the generator field duty cycle signal circuit. When the Ignition is in the RUN position and the engine is OFF, the ECM should detect a duty cycle near 0 percent. However, when the engine is running, the duty cycle should be between 5-95 percent.

### Conditions for Running the DTC

• | No generator, crankshaft position (CKP) sensor, or camshaft (CMP) sensor DTCs are set.

• | Ignition ON engine OFF, for the Ignition ON test.

• | Engine running, engine speed less than 3,000 RPM for the RUN test.

### Conditions for Setting the DTC

• | DTC P0621 is not set.

• | Ignition ON engine OFF, the ECM detects a PWM signal greater than 65 percent for 5 seconds.

• | Engine running, the ECM detects a PWM signal less than 5 percent for 15 seconds.

### Action Taken When the DTC Sets

The instrument panel cluster (IPC) illuminates the charge indicator.

### Conditions for Clearing the DTC

DTC P0622 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

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

With the scan tool installed, ignition ON and the engine running, observe the scan tool ECM GEN-F Terminal Signal parameter. The parameter should read between 5 and 95 percent.

### Circuit/System Testing

1. Verify that a test lamp illuminates between the generator output B+ circuit terminal 1 X2 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

2. Ignition OFF, disconnect the harness connector X1 at the generator.
3. Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter displays less than 5 percent.

⇒ | If greater than the specified range, test the signal circuit terminal 2 X1 for a short to voltage. If the circuit tests normal, replace the ECM.

4. Install a 3A fused jumper wire between B+ and the signal circuit.
5. Verify the scan tool ECM GEN-F Terminal Signal parameter displays greater than 95 percent.

⇒ | If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

6. If the circuit tests normal replace the generator.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Generator Replacement

• | Control Module References for ECM replacement, setup, and programming