B1428

DTC B1428

Diagnostic Instructions

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

DTC Descriptor
DTC B1428
- Ignition Switched Power Run/Crank Relay Circuit

Diagnostic Fault Information





Circuit/System Description

The body control module (BCM) controls the IGN MAIN PCB relay through the run/crank relay coil control circuit by applying voltage to the circuit. The IGN MAIN PCB relay is energized when the ignition switch is in ON or START, or when a remote start is requested.

Conditions for Running the DTC

* The system voltage is between 9-16 volts.
* The DTC can only run when the output is activated.

Conditions for Setting the DTC

The DTC will set only when the output is activated and there is a short to ground in the run/crank relay coil control circuit.

Action Taken When the DTC Sets

The module output driver will be shut down and not supply voltage to the run/crank relay coil control circuit.

Conditions for Clearing the DTC

* The current DTC will clear when the module request for the output is removed or the malfunction is no longer present.
* A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

Diagnostic Aids

* Use the DMM MIN/MAX function to capture/locate intermittent conditions.
* Short to voltage in the run/crank relay coil control circuit will cause the malfunction indicator lamp (MIL) to illuminate with the ignition key OFF, and the engine will remain running if started and the ignition key is removed.

Reference Information
Schematic Reference

* Body Control System Schematics (Electrical Diagrams)
* Power Distribution Schematics (Power Distribution Diagrams)

Connector End View Reference

Component Connector End Views (Connector Views)
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)

Circuit/System Testing

1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Test for greater than 70 ohms of resistance between the BCM run/crank relay coil control circuit terminal 21 and ground.

• If less than specified, test the control circuit for a short to ground. If the circuit tests normal, replace the underhood fuse block.

3. If the circuit tests normal, test or replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the repair.

Refer to Control Module References (Programming and Relearning) for BCM replacement, setup, and programming

Accessory Wiring Junction Block Replacement (Accessory Wiring Junction Block Replacement)