B144B
DTC B144B
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (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 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 100ms, 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 100ms. 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 Moding Schematics)Body Control System Schematics
* Power Distribution Schematics (Power Distribution Schematics)Power Distribution Schematics
Connector End View Reference
Component Connector End Views (Connector End Views By Name)Component Connector End Views
Description and Operation
Power Mode Description and Operation (Power Mode)Power Mode Description and Operation
Electrical Information Reference
* Circuit Testing (Circuit Testing)Circuit Testing
* Connector Repairs (Connector Repairs)Connector Repairs
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs (Wiring Repairs)Wiring Repairs
Scan Tool Reference
Control Module References (Programming and Relearning)Control Module References for scan tool information
Circuit/System Verification
Ignition ON, verify DTC B1330 is not set.
If the DTC is set, refer to DTC B1330 (B1330).
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.
• 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 BCM.
4. Ignition 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. Ignition ON, 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. Ignition OFF, Connect the X3 harness connector at the K9 BCM. Disconnect the KR74 ignition run relay.
7. 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 ohm between the ground circuit terminal 86 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 85 and ground.
9. Cycle the ignition ON and OFF. The test lamp should turn ON and OFF when changing ignition modes.
• 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.
10. If all circuits test normal, test or replace the KR74 ignition run relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) Diagnostic Repair Verification 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))Relay Replacement
* Control Module References (Programming and Relearning)Control Module References for BCM or keyless entry control module replacement, setup, and programming