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 P2500: Generator L-Terminal Circuit Low Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Generator Turn ON Signal | P2500 | P2500 | P2501 | --

### Circuit/System Description

The engine control module (ECM) uses the generator turn on signal circuit to control the load of the generator on the engine. A high side driver in the ECM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. When the ECM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the ECM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.

The ECM monitors the state of the generator turn on signal circuit. With the engine running, the ECM should detect a high generator turn on signal circuit.

### Conditions for Running the DTC

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

• | The engine is running.

### Conditions for Setting the DTC

The ECM detects a low signal voltage on the generator turn on signal circuit for 15 seconds.

### Action Taken When the DTC Sets

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

### Conditions for Clearing the DTC

DTC P2500 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 Testing

1. Ignition OFF, disconnect the harness connector X1 at the generator.
2. Engine running, test for greater than 3.5 V between the generator turn on signal circuit terminal B X1 and ground.

⇒ | If less than the specified range, test the generator turn on signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

3. If the circuit tests normal, test or 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