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 B1428: Ignition Switched Power Run/Crank Relay Circuit

### Circuit/System Description

The body control module (BCM) controls the IGN MAIN relay 31 by applying voltage to the circuit. The IGN MAIN relay 31 is energized when the ignition switch is in RUN 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

DTC will set when the output is activated and there is a short to ground in the circuit.

### Action Taken When the DTC Sets

The module output driver will be shut down and not supply voltage to the run/crank ignition 1 voltage 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.

### Reference Information

#### Schematic Reference

• | Power Moding Schematics

• | Power Distribution Schematics

#### Connector End View Reference

Power and Grounding Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data Definitions

• | Scan Tool Data List

### Circuit/System Testing

1. Ignition OFF, disconnect the IGN MAIN relay 31.
2. Connect a test lamp between the relay control circuit and ground.
3. Cycle the ignition ON and OFF. The test lamp should turn ON and OFF when changing ignition switch positions.

⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the BCM.

⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the IGN MAIN relay 31.

### Component Testing

1. Ignition OFF, disconnect the IGN MAIN relay 31.
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

4. Test for less then 2 ohms of resistance between terminals 30 and 87A.

⇒ | If greater then the specified range, replace the relay.

5. 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.

Control Module References for control module replacement, setup, and programming.