P0622

DTC P0622

Diagnostic Instructions
^ Perform the [Diagnostic System Check - Vehicle Diagnostic Information] prior to using this diagnostic procedure. Diagnostic System Check - Vehicle Diagnostic Information
^ Review [Strategy Based Diagnosis] for an overview of the diagnostic approach. Strategy Based Diagnosis
^ [Diagnostic Procedure Instructions - Vehicle Diagnostic Information] provides an overview of each diagnostic category. Diagnostic Procedure Instructions - Vehicle Diagnostic Information

DTC Descriptor
DTC P0622 Generator F-Terminal Circuit

Diagnostic Fault Information






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 key 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
^ The vehicle speed is above 8 km/h (5 mph).
^ The system voltage is between 9.5-18 volts.

Conditions for Setting the DTC
With the engine running, the ECM detects a PWM signal less than 5 percent for at least 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.

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 5-95 percent.

Circuit/System Testing
1. Ignition OFF, disconnect the generator harness connector.
2. Ignition ON engine OFF, connect a test lamp to B+ and repeatedly probe the generator field duty cycle circuit terminal 2, harness side while monitoring the GEN-F Terminal Signal Parameter. It should change from 0 percent to above 95 percent.
^ If the circuit tests normal, replace the generator.
^ If the parameter was not affected by the test lamp, test the circuit for a short to voltage, short to ground or an open/high resistance.

3. If the circuit tests normal, replace the ECM.

Repair Instructions
Perform the [Diagnostic Repair Verification - Vehicle Diagnostic Information] after completing the diagnostic procedure. Diagnostic Repair Verification - Vehicle Diagnostic Information
^ [Generator Replacement]