P0108

What it means

P0108 is the generic code for a high signal from the Manifold Absolute Pressure (MAP) or Barometric Pressure sensor circuit. The engine control unit saw the sensor signal voltage sit above the expected range for the operating conditions, for example close to the 5 volt reference at idle or with the engine off, when a lower reading would be normal. The cause may be the sensor, its wiring, or a real pressure problem on the intake side.

Symptoms

• Malfunction indicator lamp on
• Rough or unstable idle
• Poor acceleration or hesitation
• Black smoke or rich running with higher fuel consumption
• Hard starting or stalling
• Engine running in a reduced-performance (limp) mode

Possible causes

• Faulty MAP sensor reading high or failed internallylikely
• Signal wire shorted to the 5 volt reference or to battery voltagelikely
• Open circuit in the sensor ground wire, giving a high signal voltagelikely
• Corroded, damaged or loose connector terminals at the sensor or control unitpossible
• Blocked, split or disconnected vacuum hose to the sensor (where the sensor is remote-mounted)possible
• Fault in a shared 5 volt reference supply, for instance from another failed sensor on the same feedpossible
• Internal fault in the engine control unitrare

How to diagnose

1. Read the stored codes and freeze frame data to see engine speed, load and temperature when the fault set, and check for other sensor circuit codes that point to a shared 5 volt reference fault.
2. Visually inspect the sensor, its connector, the wiring and any vacuum hose for damage, chafing, corrosion, oil contamination or poor routing.
3. With the ignition on and engine off, view the live MAP reading; it should be close to barometric pressure for your altitude. A reading stuck at maximum suggests a high signal fault.
4. Compare the live reading with the barometric pressure and check that it falls at idle and responds smoothly to throttle changes.
5. Unplug the sensor and check the reference voltage, ground and signal wire at the harness connector against the manufacturer's data, as pin layout varies by model and engine.
6. Check the ground wire for resistance and the signal wire for a short to voltage or an open circuit, with the ignition off and the control unit connector disconnected where specified.
7. If the sensor is remote-mounted, check that the vacuum hose and port are clear and sealed, and for a sensor on the manifold check for leaks or blockages at the port.
8. Only if all wiring and the sensor test correctly, consider the control unit and follow the manufacturer's procedure to confirm the fault.

How to fix

• Replace the MAP sensor if it reads incorrectly or fails the manufacturer's voltage tests.
• Repair or replace damaged wiring, including shorts to voltage or open ground connections.
• Clean, repair or replace corroded or loose connector terminals.
• Replace any blocked, split or perished vacuum hose and clear the sensor port.
• Repair the cause of any shared 5 volt reference fault, such as a failed sensor on the same supply.
• Repair or replace the control unit only after all other causes are ruled out, and follow the manufacturer's procedure.

Can I keep driving?

Nearby codes

• P0107GenericManifold Absolute Pressure/Barometric Pressure Sensor Circuit Low
• P0109GenericManifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent