B144B
DTC B144B
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions 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/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 energized 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 [1][2]Body Control Systems
* Power Distribution Schematics Power Distribution Schematics
Connector End View Reference
Component Connector End Views Sunshade - Left (DH6)
Description and Operation
Power Mode Description and Operation Power Mode
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References 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.
• 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 omhs of resistance between terminals 1 and 2.
• If the resistance is not within the specified range, replace the KR73 ignition main relay.
3. Test for infinite resistance between the following terminals:
* 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 omhs of resistance between terminals 3 and 5.
• If greater than specified, replace the KR73 ignition main relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
Refer to Control Module References Control Module References for BCM replacement, setup, and programming