B1566

DTC B1566

Diagnostic Instructions

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



DTC Descriptors
DTC B1566
- Current Sensor Polarity Check - 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 B1566 will set.


Conditions for Running the DTC

* The engine is running.
* This diagnostic runs every 50 ms.



Conditions for Setting the DTC

The GBCM detects reverse polarity of the battery current.


Action Taken When the DTC Sets

* The charge indicator turns ON.
* The driver information center (DIC) displays the SERVICE CHARGSYS message.
* The filtered battery current is set to 0.1 amp.
* The generator field control circuit duty cycle is set to 100 percent, battery voltage defaults to 13.8 volts.



Conditions for Clearing the DTC

The GBCM detects correct polarity of the battery current.


Reference Information
Schematic Reference

Starting and Charging Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Component Connector End Views)
Description and Operation

Charging System Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information


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 using the scan tool and start the engine. Verify that DTC B1566 does not set as current.

• If the DTC sets, replace the GBCM.




Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.


Control Module References (Programming and Relearning) for GBCM replacement, setup, and programming