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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 Descriptors

DTC B144B 01
- Run/Crank Power Relay Circuit Short to Battery

DTC B144B 02
- Run/Crank Power Relay Circuit Short to Ground

DTC B144B 04
- Run/Crank Power Relay Circuit Open

Diagnostic Fault Information






Circuit/System Description

The body control module (BCM) controls the ignition run relay through the control circuit by applying voltage to the ignition run relay coil control circuit. The ignition run relay is energized when the vehicle is in Service Mode, the vehicle is ON, 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 ignition run relay through the control circuit by applying voltage to the ignition circuit. This circuit is a pass-thru in the BCM and will energize the ignition circuit when the vehicle is in Service Mode, the vehicle is ON, 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 ignition output is not active and a short to battery is detected 3 consecutive times on the ignition voltage circuit

B144B 02 - BCM

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

B144B 02 - Keyless Entry Control Module

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

B144B 04

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

Action Taken When the DTC Sets

B144B 01, B144B 04

No action is taken

B144B 02

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

Conditions for Clearing the DTC

* The current DTC will clear when the malfunction is no longer present and an ignition request is received.

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

Diagnostic Aids

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

Reference Information

Schematic Reference

Power Moding Schematics Power Moding Schematics

Connector End View Reference

Component Connector End Views Hybrid/EV Battery Pack X1

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 Programming and Relearning for scan tool information

Circuit/System Verification

1. Vehicle in Service Mode.

2. Verify the KR74 ignition run relay turns ON and OFF when commanding the run/crank relay ON and OFF with a scan tool.

• If the KR74 ignition run relay does not turn ON and OFF
Refer to Circuit/System Testing.

• If the KR74 ignition run relay turns ON and OFF

3. All OK.

Circuit/System Testing

1. Vehicle in Service Mode, disconnect the X2 harness connector at the K84 keyless entry control module.

2. Verify that a test lamp illuminates between the B+ circuit terminal 6 and ground.

• If the test lamp does not illuminate and the circuit fuse is OK

1. Vehicle OFF.

2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, verify the fuse is OK and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Vehicle OFF.

2. Test for infinite resistance between the ignition circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, replace the K84 keyless entry control module.

• If the test lamp illuminates

3. Vehicle OFF, connect the X2 harness connector at the K84 keyless entry control module and disconnect the X3 harness connector at the K9 body control module.

4. Test for less than 1 V between the ignition circuit terminal 6 and ground.

• If 1 V or greater
Repair the short to voltage on the circuit.

• If less than 1 V

5. Vehicle in Service Mode.

6. Verify a test lamp illuminates between the ignition circuit terminal 6 and ground.

• If the test lamp does not illuminate

1. Vehicle OFF.

2. Test for infinite resistance between the ignition circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance.

3. Test for less than 2 ohms in the ignition circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K84 keyless entry control module.

• If the test lamp illuminates

7. Vehicle OFF, connect the X3 harness connector at the K9 body control module.

8. Vehicle OFF and all vehicle systems OFF, disconnect the KR74 ignition run relay. It may take up to 2 minutes for all vehicle systems to power down.

9. Test for less than 10 ohms between the ground circuit terminal 85 and ground.

• If 10 ohms or greater

1. Vehicle OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

10. Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85.

11. Verify the test lamp turns ON and OFF when commanding the run/crank relay ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Vehicle OFF, disconnect the harness connector at the K9 body control module.

2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance.

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K9 body control module.

• If the test lamp is always ON

1. Vehicle OFF, disconnect the harness connector at the K9 body control module, Vehicle in Service Mode.

2. Test for less than 1 V between the control circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K9 body control module.

• If the test lamp turns ON and OFF

12. Test or replace the KR74 ignition run relay.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

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

* Control Module References Programming and Relearning for BCM or keyless entry control module replacement, programming and setup

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