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 P0625: Generator F-Terminal Circuit Low VoltageDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ | P0625 | P0625 | P0626 | -- |
Generator Field Duty Cycle Signal | P0625 | P0625 | P0626 | -- |
Circuit/System Description
The engine control module (ECM) uses the generator field duty cycle signal circuit to monitor the duty cycle of the generator and fault indication. The generator field duty cycle signal circuit connects to the high side of the field winding in the generator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field winding 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 state of the generator field duty cycle signal circuit. When the engine is running, the ECM should detect a duty cycle that varies up to 100 percent. The ECM monitors the PWM signal using a Ignition ON test and a RUN test. During the tests, if the ECM detects an out of range PWM signal, a DTC will set.
Conditions for Running the DTC
| • | The engine is running. |
| • | The engine speed is less than 3000 RPM. |
Conditions for Setting the DTC
The ECM detects a pulse width modulated (PWM) signal less than 5 percent for 15 seconds.
Action Taken When the DTC Sets
| • | The charge indicator turns ON. |
| • | The driver information center (DIC) displays the SERVICE BATTERY CHARGING SYSTEM warning message. |
Conditions for Clearing the DTC
DTC P0625 is a C type DTC.
Reference Information
Schematic Reference
Starting and Charging Schematics
Connector End View Reference
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 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
- Verify that a test lamp illuminates between the generator output B+ circuit terminal X2 and ground.
- Ignition OFF, disconnect the X1 harness connector at the generator.
- Ignition ON, verify the scan tool ECM GEN-F Terminal Signal parameter displays less than 5 percent.
- Install a 3A fused jumper wire between B+ and the signal circuit terminal 2 X1.
- Verify the scan tool ECM GEN-F Terminal Signal parameter displays greater than 95 percent.
- If the circuit tests normal replace the generator.
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
