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/Crank Relay control circuit. The Ignition Run Relay is energized when the ignition is in the ON and CRANK positions.
Conditions for Running the DTC
System voltage 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
A short to ground is detected on the Ignition Run Relay coil control 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 Run 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 mode is changed to OFF.
Reference Information
Schematic Reference
Power Moding Schematics Power Moding Schematics
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
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 Verification
1. Ignition ON.
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. Ignition OFF, disconnect the KR74 Ignition Run Relay, ignition ON.
2. Connect a test lamp between the control circuit terminal 86 and ground.
3. 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. Ignition 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. Ignition OFF, disconnect the harness connector at the K9 Body Control Module, ignition ON.
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
4. 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 Control Module References for Body Control Module replacement, programming and setup