Vehicle Access
DTC P257D-P257F
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 Instructionsprovides an overview of each diagnostic category.
DTC Descriptors
DTC P257D
- Engine Hood Switch Performance
DTC P257E
- Engine Hood Switch Circuit Low Voltage
DTC P257F
- Engine Hood Switch Circuit High Voltage
Diagnostic Fault Information
Circuit/System Description
The hood ajar switch functions as a safety device so that when the hood is open and the ignition is ON, the engine starts and runs, this is necessary to prevent the engine from starting unexpectedly when the battery voltage drops below a critical level while a technician is performing diagnostics/maintenance/repairs in the engine compartment.
When the ignition is ON, the vehicle integration control module supplies a voltage signal to the hood ajar switch through the hood ajar switch signal circuit. When the hood is opened, the signal circuit is connected to ground through the hood ajar switch ground circuit and the voltage is pulled low within the vehicle integration control module.
Conditions for Running the DTC
Battery voltage must be between 9-16 V.
Conditions for Setting the DTC
P257D
The vehicle integration control module receives a serial data message from the BCM indicating that the hood is ajar while the hood ajar signal circuit inactive.
P257E
The vehicle integration control module detects a short to ground or an open/high resistance in the hood ajar signal circuit.
P257F
The vehicle integration control module detects a short to voltage in the hood ajar signal circuit.
Action Taken When the DTC Sets
The engine will start and run whenever the ignition is ON.
Conditions for Clearing the DTC
* The DTC will be current for as long as the fault is present.
* When the fault is no longer present, the DTC will become a history DTC.
* A history DTC will clear after 50 ignition cycles
Reference Information
Schematic Reference
Release Systems Schematics
Connector End View Reference
Component Connector End Views Hybrid/EV Battery Pack X1 A4
Description and Operation
Hood Ajar Indicator Description and Operation Description and Operation
Electrical Information Reference
* 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 Referencesfor scan tool information
Circuit/System Verification
Ignition ON, observe the scan tool Hood Position Switch parameter while opening and closing the hood, the parameter should change between Open and Closed.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the B55 hood ajar switch.
2. Test for less than 30 ohm between the ground circuit terminal C and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Ignition ON, verify the scan tool VICM Hood Position Switch parameter is Closed.
• If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the A694 vehicle integration control module.
4. Install a 3 A fused jumper between the signal circuit terminal A and the ground circuit terminal C. Verify the scan tool Hood Position Switch parameter is Open.
• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the A694 vehicle integration control module.
5. If all circuits test normal, test or replace the B55 hood ajar switch.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Hood Primary and Secondary Latch Replacement Service and Repair
* Control Module References Control Module Referencesfor vehicle integration control module replacement, programming and setup