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) sensor or Barometric Pressure (BARO) sensor that is higher than the expected range. This typically means the sensor is reading a voltage above the normal operating parameters, often due to a short to voltage, a faulty sensor, or a wiring issue. The MAP sensor measures intake manifold pressure to help the ECM calculate fuel delivery and ignition timing. A high input can cause the ECM to think the engine is under heavy load, leading to rich fuel mixture, poor performance, and potential drivability issues.
01. Most Common Causes
- Faulty MAP sensor
- Short to voltage in MAP sensor signal circuit
- Damaged wiring or connector
- Faulty ECM (rare)
02. Symptoms You Will Notice
- Check Engine Light on
- Poor engine performance (hesitation, stalling)
- Rich fuel mixture (black smoke from exhaust)
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Connect a scan tool and verify the code P0108. Check freeze frame data for conditions.
Step 2: Visually inspect the MAP sensor wiring and connector for damage, corrosion, or loose pins.
Step 3: With key on engine off, measure voltage at MAP sensor signal wire (should be ~4.5-5V at sea level). If voltage is near 5V, suspect a short to reference voltage.
Step 4: Disconnect MAP sensor and check if voltage drops to 0V. If not, repair short in wiring. If voltage drops, replace MAP sensor.
Step 5: Clear codes and test drive. If code returns, check ECM for faults.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the rich fuel mixture can damage the catalytic converter and cause poor drivability. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a MAP sensor replacement, including parts and labor. Diagnostic fees may add $50-$100.