Quick answer: The P0108 code indicates that your vehicle’s Manifold Absolute Pressure (MAP) sensor is sending an abnormally high voltage signal to the engine control module. This affects the fuel delivery and ignition timing systems. While you can drive short distances, immediate inspection is required to avoid severe engine misfires or catalytic converter damage.
Seeing the check engine light turn on alongside code P0108 can be intimidating, especially if your engine is idling roughly or hesitating during acceleration. This diagnostic trouble code points directly to a high voltage signal from your intake manifold pressure sensor circuit. In this guide, we will break down what causes this issue, how to spot the symptoms, and the exact steps to fix it safely.
What Does P0108 Mean?
P0108 stands for “Manifold Absolute Pressure (MAP) Sensor Circuit High Input.” Your engine control module relies on the MAP sensor to measure vacuum pressure inside the intake manifold, which tells the system how much load the engine is under. When the voltage signal sent from this sensor stays above normal operating limits (typically above 4.5 volts), the computer assumes maximum engine load or a circuit failure. As a result, the engine control module compensates by adding excessive fuel into the combustion chambers, leading to a rich air-fuel mixture.
Symptoms
- Illuminated check engine light on the dashboard
- Rough, shaking, or unstable engine idling
- Engine hesitation or stumbling during acceleration
- Noticeable decrease in fuel economy
- Black smoke discharging from the exhaust pipe
- Engine stalling when slowing down or coming to a complete stop
Possible Causes
Replacing the MAP sensor immediately is a common mistake; often, simple wiring issues or vacuum leaks are the true cause.
- Disconnected, cracked, or pinched vacuum hose leading to the MAP sensor
- Damaged, shorted, or corroded wiring in the MAP sensor harness
- Loose, dirty, or bent pins in the sensor connector
- Faulty MAP sensor failing internally
- Faulty Powertrain Control Module (PCM), though this is rare
Check These Yourself Before Visiting a Mechanic
- Inspect the small rubber vacuum hose connected to the MAP sensor for cracks, splits, or loose fits.
- Check the electrical connector attached to the MAP sensor to ensure it is firmly snapped in and free of green corrosion or oil buildup.
- Examine the wiring harness near the sensor for visible fraying, chafing, or spots melted against hot engine components.
How to Fix It
- Connect an OBD-II scanner to read live MAP sensor voltage with the engine running.
- Inspect and replace any compromised vacuum lines supplying the sensor.
- Test the sensor harness with a multimeter to verify 5-volt reference power, ground, and signal ground integrity.
- Repair or clean damaged wiring, ground connections, or harness plug pins.
- Replace the MAP sensor if reference voltage and vacuum lines are sound, but output voltage remains fixed high.
- Clear the diagnostic trouble codes and complete a road test to ensure the system re-evaluates correctly.
Estimated Repair Costs (2026)
| Job | Parts ($) | Labor ($) |
|---|---|---|
| Vacuum Hose Replacement | $10 – $30 | $50 – $100 |
| Wiring or Connector Repair | $15 – $40 | $75 – $150 |
| MAP Sensor Replacement | $40 – $150 | $50 – $120 |
| Diagnostic Inspection Fee | $0 | $90 – $150 |
Note: these are 2026 estimates in US dollars; costs vary by make and model.
Frequently Asked Questions
Can I drive with the P0108 code?
You should only drive a short distance to reach a safe place or repair shop. Because P0108 causes the engine to run excessively rich, prolonged driving can unburnt fuel down the exhaust, which quickly destroys your catalytic converter and fouls your spark plugs.
How do I clear the P0108 code?
You can clear the code using an OBD-II scanner after repairing the underlying issue. If you clear the code without addressing the short circuit or faulty sensor, the check engine light will return within a few key cycles.
Can a dirty throttle body cause a P0108 code?
While a dirty throttle body can alter intake airflow and cause rough idling, it rarely sets off a P0108 code directly. P0108 specifically signals a high voltage condition, which typically points to circuit shorts, sensor failure, or a complete loss of manifold vacuum to the sensor.