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 Descriptors

DTC B151B: Current Sensor Polarity Error - GBCM

### Circuit/System Description

The generator battery control module (GBCM) monitors its internal battery current sensor for many charging system operations, and also for diagnostic purposes. If reversed polarity of the battery current is sensed, then DTC B151B will set.

### Conditions for Running the DTC

• | The engine is not running.

• | DTC B1516 is not set.

### Conditions for Setting the DTC

The GBCM detects positive battery current.

### Action Taken When the DTC Sets

The regulated voltage control (RVC) is disabled.

### Conditions for Clearing the DTC

The GBCM detects correct polarity of the battery current.

### Diagnostic Aids

DTC B151B may set if a battery charger is used.

### Reference Information

#### Schematic Reference

Starting and Charging Schematics

#### Connector End View Reference

Engine Electrical 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

• | Scan Tool Output Controls

• | Scan Tool Data List

• | Scan Tool Data Definitions

### Circuit/System Verification

1. Verify that the GBCM is installed correctly. The GBCM should be installed on the negative battery cables, with the sensor coil around the negative cables and facing away from the battery, and with the harness connector facing toward the battery.

⇒ | If the GBCM is installed backwards or incorrectly, remove and reinstall the GBCM.

2. Ignition ON, clear the DTC with the scan tool. Verify that DTC B151B does not set.

⇒ | If the DTC sets, replace the GBCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for GBCM replacement, setup, and programming.