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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

Vehicle in Service Mode, verify DTC B1330 is not set.

If the DTC is set, refer to DTC B1325, B1330, B1517, C0800, C0899, C0900, C12E1, C12E2, P0562, P0563, P1A0C, P1A0D, or P1EFC B1325.

Circuit/System Testing

1. Vehicle 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.

• 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.

3. Connect the X2 harness connector at the K84 keyless entry control module. Disconnect the X3 harness connector at the K9 body control module.
4. Vehicle OFF, test for less than 1 V between the ignition circuit terminal 6 and ground.

• 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.

5. Vehicle in Service Mode, verify that a test lamp illuminates between the ignition circuit terminal 6 and ground.

• 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.

6. Vehicle OFF, Connect the X3 harness connector at the K9 body control module. Disconnect the KR74 ignition run relay.
7. Vehicle 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 ohm between the ground circuit terminal 85 and ground.

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

8. Connect a test lamp between the control circuit terminal 86 and ground.
9. Cycle between Service Mode and vehicle OFF. The test lamp should turn ON and OFF when changing Service Modes and vehicle OFF.

• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 body control module.
• 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 body control module.

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

Component Testing

1. Vehicle OFF, disconnect the KR74 ignition run relay.
2. Test for 70-150 Ohms between terminals 85 and 86.

• If the resistance is not within the specified range, replace the KR74 ignition run relay.

3. Test for infinite resistance between the following terminals:

* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87

• If less than specified, replace the KR74 ignition run relay.

4. Install a 3 A fused jumper wire between relay terminal 86 and 12 V. Install a jumper wire between relay terminal 85 and ground. Measure for less than 5 Ohms between terminals 87 and 30.

• If greater than specified, replace the KR74 ignition run relay.

Repair Instructions

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

* Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)
* Control Module References Programming and Relearning for BCM or keyless entry control module replacement, programming and setup

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