GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P254F: Engine Hood Switch Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Hood Ajar Switch Signal

P254F

P254F

P254F

--

Hood Closed Switch Signal

P254F

P254F

P254F

--

Ground

--

P254F

--

--

Circuit/System Description

The engine control module (ECM) monitors the voltage input of the hood open switch signal circuit and the hood open closed switch signal circuit. With the hood open, the hood ajar portion of the switch is closed, grounding the hood ajar switch signal circuit from the ECM, and the hood closed portion of the switch is open. With the hood closed, the hood closed portion of the switch is closed, grounding the hood closed switch signal circuit from the ECM, and the hood ajar portion of the switch is open. During proper operation, the two separate voltage signals at the ECM should never be at the same voltage.

Conditions for Running the DTC

The ECM continuously monitors for this DTC

Conditions for Setting the DTC

Both the hood open switch signal circuit and the hood closed switch signal circuit are simultaneously in an active or inactive state.

Action Taken When the DTC Sets

Engine starting will be disabled.

Conditions for Clearing the DTC

    • A current DTC will clear when the conditions for setting are no longer present.
    • A history DTC will clear after 40 malfunction free ignition cycles.

Reference Information

Schematic Reference

Immobilizer Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Keyless Entry System Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool ECM Hood Position parameter. With the hood open, the Hood Position parameter should read Open. With the hood closed, the Hood Position parameter should read Closed.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the hood ajar switch.
  2. Ignition OFF, test for less than 10 ohms between the ground circuit terminal C and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, test for 10.0-12.5 volts between the signal circuit terminal A and ground.
  5. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. Ignition ON, test for 10.0-12.5 volts between the signal circuit terminal B and ground.
  7. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  8. If all circuits test normal, test or replace the hood ajar switch.

Component Testing

Hood Ajar Switch

  1. Ignition OFF, disconnect the harness connector at the hood ajar switch.
  2. With the switch in the hood closed position, test for infinite resistance between the ground terminal C and the signal terminal A.
  3. If not infinite, replace the hood ajar switch.
  4. Test for less than 2.0 ohms between the ground terminal C and the signal terminal B.
  5. If greater than the specified range, replace the hood ajar switch.
  6. With the switch in the hood open position, test for infinite resistance between the ground terminal C and the signal terminal B.
  7. If not infinite, replace the hood ajar switch.
  8. Test for less than 2.0 ohms between the ground terminal C and the signal terminal A.
  9. If greater than the specified range, replace the hood ajar switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Hood Primary and Secondary Latch Replacement
    •  Control Module References for ECM replacement, programming and setup