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 B1488: Generator L-Terminal Circuit High

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Generator Turn On Signal | B1487 | -- | B1488 | --

### Circuit/System Description

The generator battery control module controls the generator through the generator turn on signal circuit. The signal is a 5-volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is 0 percent when the engine is not running. If the generator turn on signal circuit is 65 percent or greater duty cycle, or shorted to voltage, then DTC B1488 will set.

### Conditions for Running the DTC

• | The ignition is ON.

• | The engine is OFF.

• | This diagnostic runs every 100 ms.

### Conditions for Setting the DTC

The generator turn on signal circuit duty cycle is greater than 65 percent for 5 seconds.

### Action Taken When the DTC Sets

• | The charge indicator turns ON.

• | The driver information center (DIC) displays the SERVICE CHARGE SYS message.

### Conditions for Clearing the DTC

• | The DTC will pass when the conditions for setting the DTC are no longer present.

• | The charge indicator and DIC message will remain ON until the ignition is cycled after clearing the 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

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the generator.
2. Ignition ON, test for less than 1 volt between the generator turn on signal circuit terminal 1 X1 and ground.

⇒ | If greater than the specified range, test the generator turn on signal circuit for a short to voltage. If the circuit tests normal, replace the GBCM.

3. Engine Running, test for greater than 3 volts between the generator turn on signal circuit terminal 1 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 GBCM.

4. 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 GBCM replacement, setup, and programming.