P0108: MAP/Barometric Pressure Circuit High Input
The P0108 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the Manifold Absolute Pressure (MAP) or Barometric Pressure (BARO) sensor that is higher than the expected range. This typically means the sensor is reading an abnormally high pressure, which can be caused by a faulty sensor, wiring issues, or a vacuum leak. The ECM uses this sensor to calculate engine load and fuel delivery, so an incorrect reading can lead to poor performance and increased emissions.
1. Most Common Causes
- Faulty or internally worn MAP sensor
- MAP circuit wiring shorted to reference voltage (5V) or battery voltage (B+)
- MAP circuit wiring shorted to ground on the low-voltage signal side
- Corroded, damaged, or bent pins in the MAP sensor connector
- Vacuum leak in the MAP sensor hose (if hose-type design)
- Engine Control Module (ECM/PCM) failure (rare but possible)
- Excessive resistance in the MAP sensor ground circuit
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine running rich or lean
- Poor acceleration or hesitation
- Decreased fuel economy
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data.
Step 2: Visually inspect MAP sensor and wiring for damage or corrosion.
Step 3: Test MAP sensor voltage with a multimeter (should be ~0.5-4.5V depending on pressure).
Step 4: Compare sensor reading to actual manifold pressure using a vacuum gauge.
Step 5: If sensor is faulty, replace it and clear the code.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as it can cause poor fuel economy and potential engine damage due to incorrect air-fuel mixture.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, depending on the vehicle and shop rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.