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DTC B144B

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 B144B 01 : Run/Start Power Relay Circuit Short to Battery

DTC B144B 02 : Run/Start Power Relay Circuit Short to Ground

DTC B144B 04 : Run/Start Power Relay Circuit Open

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Ignition Main Relay Control

B144B 02

B144B 04, 1

B144B 01, 2

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1. No Start.

2. Vehicle will start and continue to run after the ignition key is removed.

Circuit/System Description

The body control module (BCM) controls the ignition main relay through the control circuit by applying voltage to the circuit. The ignition main relay is energised 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 V.
    • The DTC can only run when the output is activated.

Conditions for Setting the DTC

The BCM detects a short to ground in the ignition main relay control circuit.

Action Taken When the DTC Sets

The module output driver will be shut down and not supply voltage to the ignition main relay 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

Short to voltage in the ignition main relay control circuit will cause the malfunction indicator lamp (MIL) to illuminate with the ignition key OFF, and the engine will remain running if started and the ignition key is removed.

Reference Information

Schematic Reference

    •  Body Control System Schematics
    •  Power Distribution Schematics

Connector End View Reference

Component Connector End Views

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

Control Module References for scan tool information

Circuit/System Testing
  1. Ignition OFF, disconnect the KR73 ignition main relay.
  2. Connect a test lamp between the relay control circuit terminal 1 and ground.
  3. Cycle the ignition ON and OFF. The test lamp should turn ON and OFF when changing S39 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 K9 BCM.
    ⇒If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K9 BCM.
  4. If all circuits test normal, test or replace the KR73 ignition main relay.

Component Testing
  1. Ignition OFF, disconnect the KR73 ignition main relay.
  2. Test for 70-150 Ω of resistance between terminals 1 and 2.
    3. ⇒If the resistance is not within the specified range, replace the KR73 ignition main relay.
  3. Test for infinite resistance between the following terminals:
    4. • 1 and 3
    • 2 and 3
    • 2 and 5
    • 3 and 5
    ⇒If less than specified, replace the KR73 ignition main relay.
  4. Install a 3 A fused jumper wire between relay terminal 2 and 12 V. Install a jumper wire between relay terminal 1 and ground. Measure for less than 5 Ω of resistance between terminals 3 and 5.
    5. ⇒If greater than specified, replace the KR73 ignition main relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Refer to Control Module References for BCM replacement, setup, and programming

   


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