GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Sierra Denali 🢒 DTC 🢒 DTC B1428

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 Run/Crank relay by applying voltage to the circuit. The Run/Crank relay 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 Run/Crank relay.
  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.
    4. ⇒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 Run/Crank relay.

Component Testing
  1. Ignition OFF, disconnect the Run/Crank relay.
  2. Test for 70-150 ohms of resistance between terminals 85 and 86.
    3. ⇒If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals:
    4. • 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.
    5. ⇒ 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.
    6. ⇒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