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, P0625 | P0622, P0625 | -- | --
Field Duty Cycle Signal | P0622, P0625 | P0622, P0625 | P0626 | --
Turn On Signal | P0621 | -- | P0621 | --

### Circuit/System Description

The engine control module (ECM) uses the generator field duty cycle signal circuit, or F-terminal 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 ON and the engine is OFF, the ECM should detect a duty cycle near 0 percent. When the engine is running, the duty cycle should be between 5-99 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 that is greater than 65 percent for 5 seconds.

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

### Action Taken When the DTC Sets

DTC P0622 is a C type DTC.

### Conditions for Clearing the DTC

DTC P0622 is a C type DTC.

### Reference Information

#### Schematic Reference

• | Starting and Charging Schematics

• | Engine Controls Schematics for the 1.6L (LDE) and 1.8L (2HO) engine

#### 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

Engine running, observe the scan tool GEN-F Terminal Signal parameter. The GEN-F Terminal Signal parameter should display between 5-95 percent.

### Circuit/System Testing

1. Verify that a test lamp illuminates between the B+ circuit terminal B 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 X1 harness connector 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 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 a short to ground or 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