The P0108 code means the MAP sensor circuit is reading a higher-than-expected input. In practice, this points to a MAP sensor fault, wiring issues, or a vacuum/pressure problem in the intake system that’s causing the sensor to report an abnormally high signal to the engine computer.
What P0108 Means
P0108 stands for the Manifold Absolute Pressure (MAP) sensor circuit high input. The engine control module (ECM/PCM) expects a voltage from the MAP sensor that corresponds to the engine’s intake manifold pressure. When the signal is higher than the expected range, the PCM triggers P0108. This can affect idle quality, engine performance, and fuel economy. Diagnosing P0108 involves confirming sensor readings, testing the sensor, and checking related vacuum lines and wiring.
Common causes
The following list covers the usual culprits behind P0108. Each item can produce a high MAP signal if it fails or becomes faulty.
- Faulty MAP sensor itself (sensor can be stuck high or give erratic readings)
- Shorts to power or faulty ground in the MAP sensor circuit
- Vacuum hose or line leaks, disconnections, or a disconnected intake vacuum hose
- Intake manifold leaks or intake gasket issues causing abnormal pressure readings
- PCM/ECM fault or faulty data line to the MAP sensor (rare)
Diagnosing should start with the simplest checks and progress to component testing to avoid unnecessary replacements.
Diagnostic steps
The following steps guide you from basic checks to targeted testing. Do these with the engine off when inspecting wiring, and with engine running when checking live data after starting.
- Use an OBD-II scanner to confirm P0108 and view live MAP sensor data (voltage and calculated MAP pressure) across idle, revs, and load conditions.
- Inspect the MAP sensor and its wiring/connectors for signs of damage, corrosion, loose pins, or aftermarket modifications that could affect readings.
- Test the MAP sensor voltage output: with the engine off, the sensor should show a reference voltage (often 5V on the signal circuit). With the engine running, observe the voltage change as you apply vacuum to the sensor or as the throttle opens. Compare readings to the vehicle’s service manual specifications.
- Check all vacuum lines and hoses connected to the MAP sensor and intake for cracks, holes, or disconnections. Repair or replace as needed.
- Look for intake manifold or gasket leaks using methods such as spray testing (careful to avoid ignition sources) or soapy-water/traceant while the engine runs to identify leaks.
- Inspect the power supply and ground for the MAP sensor circuit: verify fuse integrity and check the sensor’s ground path for continuity to the pcm/engine block.
- If the MAP sensor tests normal and no leaks are found, consider a PCM data-line issue or a rare PCM fault. In such cases, consult a professional with wiring diagrams for your specific vehicle.
After performing these checks, you should have a clearer picture of whether the fault lies with the sensor, the wiring, or the vacuum system. Document readings and compare them to the manufacturer's specifications for your exact make/model.
Repair options
Repair decisions depend on the diagnosed cause. The following options cover the most common outcomes after testing.
- Replace the MAP sensor if it’s proven to be defective or stuck high
- Repair or replace damaged MAP sensor wiring or connectors; fix any shorts or corrosion
- Repair or replace vacuum hoses or lines that are cracked, disconnected, or leaking
- Repair intake manifold leaks or faulty gaskets to restore correct manifold pressure
- Address any PCM/data-line issues if diagnostics indicate a calibration or wiring fault
After any repair, clear the code with a scan tool, run the engine through a few drive cycles, and re-check for P0108 to confirm the issue is resolved.
When to seek professional help
If you’re uncomfortable performing electrical tests or vacuum testing, or if the code reappears after your repairs, seek a qualified mechanic. Some vehicles require factory diagnostic tools and service manuals to interpret MAP sensor specifications and wiring diagrams accurately.
Summary
P0108 signals that the MAP sensor circuit is reading a higher-than-expected input. Start with a visual inspection of MAP sensor and wiring, test the sensor’s voltage response, and check for vacuum leaks or manifold issues. Replace faulty components as indicated by diagnostic results, reset the code, and verify by road testing. A methodical approach minimizes unnecessary part replacement and helps restore proper engine performance.
Can I drive with a bad MAP sensor?
Can You Drive with a Bad MAP Sensor. Technically, yes — but it's not a good idea. Driving with a malfunctioning MAP sensor compromises your fuel economy and may eventually damage the engine or catalytic converter.
How do I reset my MAP sensor?
Reset the MAF sensor by idling your engine without the sensor installed for at least 10 seconds. You can also reset the MAF sensor by removing the negative battery terminal and waiting 10 minutes. You may be able to drive without the MAF sensor, but it's bad for your engine to drive without the sensor for too long.
Can a vacuum leak cause a P0108 code?
Loose connectors, moisture buildup in the wire harness and frayed wires are all common issues that could cause error code P0108. Finally, if your sensor is working properly, there may be a vacuum leak in your engine. Check the vacuum hoses and connectors to ensure a proper seal.
Can I clean my MAP sensor with brake clean?
Never use carburetor or brake cleaners, as they can damage the sensor.