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For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 LaCrosse 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 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 Relay 1 Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Ignition 1 Voltage (relay control)

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 (L26, L32) or IGNITION MAIN PCB Relay (LS4) 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 .
    • There are different fuse blocks and different relays between the LS4 (V8) engine and the L26/L32 (V6) engines. Be sure to use the correct references and diagnostic tests listed below.

Reference Information

Schematic Reference

    •  Engine Controls Schematics for the 3.8L engine
    •  Engine Controls Schematics for the 5.3L engine

Connector End View Reference

Component Connector End Views

Electrical Information Reference

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

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Testing

L26, L32

  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.
  3. Connect a test lamp between the ignition 1 voltage circuit terminal A8 and ground.
  4. 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.
    5. ⇒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.
  5. If all circuits test normal, test or replace the IGN 1 relay.

LS4

  1. Ignition OFF, disconnect the harness connector X1 of the underhood fuse block.
  2. Test for less than 1 ohm of resistance between the IGNITION MAIN PCB Relay ground circuit terminal C2 and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Disconnect the harness connector X4 of the underhood fuse block.
  4. Connect a test lamp between the ignition 1 voltage circuit terminal H1 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.
  6. If all circuits test normal, test or replace the underhood fuse block.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement
    •  Control Module References for module replacement, setup, and programming
    •  Underhood Electrical Center or Junction Block Replacement