P0108: Manifold Absolute Pressure Sensor High Input

What it means

The MAP sensor reports a pressure above the upper threshold the ECU expects in any engine state. Typically caused by a short in the signal circuit or a sensor that has failed producing a fixed high output.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The MAP sensor measures intake manifold pressure and sends the ECM a signal used to calculate engine load. P0108 sets when that signal exceeds the expected upper threshold, often because the signal wire is shorted toward supply voltage or the sensor ground is broken.

Common causes

Most likely first.

1. Signal wire shorted to supply voltage
2. MAP sensor failed
3. Sensor ground broken

Symptoms

• Check engine light on

How to diagnose it

1. Check freeze-frame and live MAP readings at key-on engine-off and idle to see whether the signal is fixed high or remains above the plausible range.
2. Inspect the MAP connector and harness for corrosion, bent pins, loose connections, or damage that could interrupt sensor ground or contact a supply wire.
3. Use the wiring diagram to test sensor ground and reference supply against the manufacturer's specification.
4. Test the signal circuit for a short to supply voltage and check continuity between the sensor and ECM as directed by the manufacturer's procedure.
5. Inspect any MAP hose and sensor port for blockage or other pressure-path problems that could contribute to an implausible reading.
6. If wiring and the pressure path check out, test the MAP sensor output against the manufacturer's specification and replace it if it stays high.

Common fixes

• Repair a broken MAP sensor ground or poor ground connection.
• Repair a signal wire shorted to supply voltage or other damaged wiring.
• Clean corroded connector terminals or replace terminals that cannot make sound contact.
• Clear a blocked MAP sensor port using an appropriate method.
• Replace a MAP sensor that continues to produce a high output with a correctly tested circuit.

Can I keep driving?

Limit driving to a short, gentle trip if the engine runs smoothly; an incorrect load estimate can cause poor fueling, hesitation, or stalling. Stop if the engine runs erratically or loses power.