B1428

DTC B1428

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

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview






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.

Circuit/System Testing

1. Ignition OFF, disconnect the IGN MAIN PCB relay and connect a test lamp between the relay control circuit and ground.
2. Cycle the ignition ON and OFF. The test lamp should turn ON and OFF when changing ignition switch positions.

• If the test lamp remains OFF all the time, test for a short to ground or an open/high resistance on the relay control circuit. If the circuit tests normal, replace the BCM.

• If the test lamp remains ON all the time, test for a short to voltage on the relay control circuit. If the circuit tests normal, replace the BCM.

3. If test lamp turns ON and OFF normal, test or replace the IGN MAIN PCB relay.

Component Testing

1. Ignition OFF, disconnect the IGN MAIN PCB relay.
2. Test for 70-150 ohms of resistance between terminals 85 and 86.

• If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87

• If less than infinite resistance, replace the relay.

4. Install a 3-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Measure for less than 2 ohms of resistance between terminals 30 and 87.

• If greater than 2 ohms, replace the relay.

Repair Instructions

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

Refer to Programming and Relearning Programming and Relearning