B0138
Hood Ajar Switch Circuit Malfunction
Lowsensor
Overview
The B0138 diagnostic trouble code indicates that the body control module has identified a hood ajar switch circuit malfunction issue. This code means a body sensor or its circuit is not providing expected readings. Accurate sensor data is important for proper operation of safety and convenience systems throughout the vehicle.
Symptoms
- Window pinch protection not functioning
- Airbag warning light on
- Rain-sensing wipers not activating automatically
- Blind spot monitoring warning not appearing
Common Causes
- Door ajar switch stuck or misaligned
- Camera lens obstructed or damaged
- Damaged sensor wiring or connector
- Sensor out of calibration
Diagnosis Steps
- 1Connect an OBD-II scanner and read all stored body control module trouble codes
- 2Inspect the affected sensor and its wiring connector for damage or corrosion
- 3Test the sensor resistance or voltage output with a multimeter
- 4Check for physical obstructions, contamination, or misalignment of the sensor
- 5Verify sensor calibration using scan tool where applicable
Estimated Repair Cost
$50 — $400
Cost varies by vehicle, location, and repair shop. Includes parts and labor.
Commonly Affected Vehicles
Toyota CorollaHonda CivicToyota RAV4Ford Explorer
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LowFrequently Asked Questions
A stuck or misaligned door ajar switch is the most common cause. The switch is located in the door latch mechanism and can be cleaned or replaced for $20-$100.