B1451
DTC B1451
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 B1451 01
- Accessory Power Circuit Short to Battery
DTC B1451 02
- Accessory Power Circuit Short to Ground
DTC B1451 04
- Accessory Power Circuit Open
Diagnostic Fault Information
Circuit/System Description
The Keyless Entry Control Module provides as a backup control for the ignition power circuit, by applying voltage to the ignition power circuit. The ignition power circuit is energized when the vehicle power mode is in ACCESSORY mode or Ignition ON mode.
Conditions for Running the DTC
B1451 01, B1451 04
* Vehicle power mode is Ignition OFF
* Module is awake
* DTC B1451 not already set
* System voltage between 6 and 16 V
B1451 02
* Vehicle power mode is ACCESSORY or Ignition ON mode
* Module is awake
* The DTC is only run when the output is active
* DTC B1451 is not already set
* System voltage between 6 and 16 V
Conditions for Setting the DTC
B1451 01
Ignition output is not active and a short to battery is detected 3 consecutive times.
B1451 02
Ignition output is active and a short to ground is detected 3 consecutive times.
B1451 04
Ignition output is not active and an open circuit is detected 20 consecutive times.
Action Taken When the DTC Sets
B1451 02
The ignition output is deactivated when a short to ground is detected. After 100 ms the output is activated again. This happens 3 times and then the output is deactivated until a new ACCESSORY or Ignition ON mode request is received.
B1451 01, B1451 04
No action is taken.
Conditions for Clearing the DTC
* The current DTC will clear when the malfunction is no longer present during a DTC check.
* A history DTC clears when the module power mode cycle counter reaches the reset threshold of 40, without a repeat of the malfunction.
Diagnostic Aids
* A short to voltage in the ignition control circuit will keep the vehicle modules awake, which can drain the vehicle's battery.
* A short to ground in the extension of this circuit through the Body Control Module can back feed to the Keyless Entry Control Module. Check for a short to ground on the ignition circuit on the other side of the ignition pass thru, in the Body Control Module, before replacing the Body Control Module.
Reference Information
Schematic Reference
Power Distribution Schematics Power Distribution Schematics
Connector End View Reference
Component Connector End Views Outside Rearview Mirror - Driver
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. Verify DTC B1330 is not set.
• If the DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
• If the DTC is not set
2. Refer to Circuit/System Testing.
Circuit/System Testing
1. Ignition ON, disconnect the X2 harness connector at the K84 Keyless Entry Control Module.
2. Verify a test lamp illuminates between the B+ circuit terminal 5 and ground.
• If the test lamp does not illuminate and the circuit fuse is OK
1. Ignition 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. Ignition 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. Ignition 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 5 and ground.
• If 1 V or greater
Repair the short to voltage on the circuit.
• If less than 1 V
5. Ignition ON.
6. Verify a test lamp illuminates between the ignition circuit terminal 5 and ground.
• If the test lamp does not illuminate
1. Ignition 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. Replace the K9 Body Control Module.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
Control Module References Control Module References for the appropriate control module replacement, programming and setup