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PRE-RELEASE

DTC B144B

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 Descriptors

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
Run/Crank Ignition 1 Voltage B144B 02* B144B 04* B144B 01* -
Run/Crank Relay Coil Control B144B 02** 1 2 -
1. No Start 2. Engine will continue to run after the igniting is turned OFF * DTC set in keyless entry control module ** DTC Set in BCM


Circuit/System Description

The body control module (BCM) controls the RUN/CRNK relay through the control circuit by applying voltage to the run/crank relay coil control circuit. The ignition RUN/CRNK is energized when the ignition mode is ON or START, or when a remote start is requested. This is part of the BCM's primary function in controlling the vehicle power mode.

The keyless entry control module controls the backup power for the RUN/CRNK relay through the control circuit by applying voltage to the run/crank ignition 1 voltage circuit. This circuit is a pass-thru in the BCM and will energize the RUN/CRNK when the ignition mode is ON or START, or when a remote start is requested.

Conditions for Running the DTC

System voltage is greater than 9 V

Conditions for Setting the DTC

B144B 01

The run/crank output is not active and a short to battery is detected 3 consecutive times on the run/crank ignition 1 voltage circuit

B144B 02 - BCM

A short to ground is detected on the run/crank relay coil control circuit

B144B 02 - Keyless Entry Control Module

The run/crank output is active and a short to ground is detected 3 consecutive times on the run/crank ignition 1 voltage circuit

B144B 04

The run/crank output is not active and an open is detected 20 consecutive times on the run/crank ignition 1 voltage circuit

Action Taken When the DTC Sets

B144B 01, B144B 04

No action is taken

B144B 02

The RUN/CRANK relay is deactivated when the fault is set. After 100 ms, the RUN/CRANK relay will be activated. If the fault is still set, the relay will be deactivated. The RUN/CRANK relay will again be activated after 100 ms. If this also results in a fault, the relay will be deactivated until a new run/crank request is received.

Conditions for Clearing the DTC


• The current DTC will clear when the malfunction is no longer present and a run/crank request is received.

• A history DTC will clear after 40 malfunction free ignition cycles.


Diagnostic Aids

A short to voltage on the run/crank relay coil control will cause the engine to remain running after the ignition mode is changed to OFF.

Reference Information

Schematic Reference


• Power Moding 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 Verification

Ignition ON, verify DTC B1330 is not set.

Circuit/System Testing


1. Ignition OFF, disconnect the X2 harness connector at the K84 keyless entry control module.

2. Verify that a test lamp illuminates between the B+ circuit terminal 5 and ground.

3. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the B+ circuit fuse is open, test the B+ circuit for a short to ground.

4. Connect the X2 harness connector at the K84 keyless entry control module. Disconnect the X3 harness connector at the K9 BCM.

5. Ignition OFF, test for less than 1 V between the ignition circuit terminal 6 and ground.

6. If greater than the specified range, test the ignition circuit for a short to voltage. If the circuit tests normal, replace the K84 keyless entry control module.

7. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal 6 and ground.

8. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K84 keyless entry control module.

9. Ignition OFF, Connect the X3 harness connector at the K9 BCM. Disconnect the KR74 ignition run relay.

10. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10 Ω between the ground circuit terminal 86 and ground.

11. If greater than the specified range, test the ground circuit for an open/high resistance.

12. Connect a test lamp between the control circuit terminal 85 and ground.

13. Cycle the ignition ON and OFF. The test lamp should turn ON and OFF when changing ignition modes.

14. 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.

15. 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.

16. If all circuits test normal, test or replace the KR74 ignition run relay.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.


• Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)

• Control Module References for BCM or keyless entry control module replacement, setup, and programming


PRE-RELEASE