GM Service Manual Online
For 1990-2009 cars only

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 Relay 1 Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Ignition 1 Voltage

B1428

B1428

1

--

Ground

--

B1428

--

--

1. DTC B1428 may or may not set for a short to voltage depending on the ignition key position when the short occurred.

Circuit Description

The body control module (BCM) controls the IGN 1 Relay which is located in the underhood fuse block. The switch contacts of the relay deliver a B+ signal to the following components:

    • The antilock brake system (ABS) functions
    • The AC compressor relay
    • The crank relay
    • The HVAC control head
    • The instrument panel cluster (IPC)
    • The powertrain control module (PCM)
    • The sensing and diagnostic module (SDM)
    • The transmission solenoids

The BCM will energize the relay when the vehicle is in the RUN or CRANK power mode. The BCM supplies B+ on the ignition 1 voltage circuit (control circuit) to energize the relay. The relay ground circuit is from G113. If a short or open/high resistance in the ignition 1 voltage circuit or an open in the ground circuit occurs, the BCM will set a B1428 and the relay will not energize.

Conditions for Running the DTC

The ignition switch is in the RUN or CRANK position

Conditions for Setting the DTC

    • A DTC B1428 sets when the BCM detects a short to ground in the ignition 1 voltage circuit of the relay when the output is controlled active.
    • A DTC B1428 sets when the BCM detects an open in the ignition 1 voltage circuit of the relay when the output is inactive.
    • The conditions above must be present for more than 0.3 second.

Action Taken When the DTC Sets

The BCM stores DTC to memory.

Conditions for Clearing the DTC

    • A current DTC clears on the next malfunction-free cycle.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids

A history DTC maybe caused by an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections .

Reference Information

Schematic Reference

    •  Engine Controls Schematics for the 3.8L engine
    •  Engine Controls Schematics for the 3.6L engine

Connector End View Reference

Master Electrical Component List

Description and Operation

Power Mode Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Scan Tool Output Controls

Circuit/System Testing

  1. Ignition OFF, disconnect the IGN 1 Relay 37.
  2. Test for less than 1 ohm of resistance between the ground circuit terminal C7 and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Connect a test lamp between the ignition 1 voltage circuit terminal A8 and ground.
  5. Command the Ignition Power Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
  6. If the test lamp is always ON, test the ignition 1 voltage 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.
  7. If all circuits test normal, test or replace the IGN 1 relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Control Module References for module replacement, setup, and programming