What Does P0108 Mean?
The manifold absolute pressure sensor circuit is outputting a voltage above the maximum expected threshold. The PCM sees a reading that indicates an impossibly low vacuum (near or above atmospheric pressure) while the engine is running, which should not occur under normal conditions. This typically indicates a short to voltage, an open vacuum reference, or a failed sensor. The driver will notice rich running, black smoke, poor economy, and poor performance.
Common Causes
30%
Disconnected or leaking vacuum hose to the MAP sensor (sensor reads atmospheric)
25%
Short to voltage in the MAP sensor signal wire
20%
Faulty MAP sensor outputting maximum voltage
15%
Clogged MAP sensor vacuum port (sensor sees atmospheric instead of manifold vacuum)
10%
Extremely large vacuum leak causing near-atmospheric manifold pressure
Diagnostic Steps
1
Check the MAP sensor PID at idle — it should read 50-75 kPa (15-22 inHg vacuum); a reading at or near 100 kPa (atmospheric) confirms the high condition.
2
Verify the MAP sensor vacuum hose is connected and not cracked — a disconnected hose is the most common and simplest cause; the sensor simply reads atmospheric pressure.
3
With the vacuum hose confirmed good, apply vacuum to the MAP sensor with a hand vacuum pump — the voltage should decrease as vacuum increases; if the voltage stays high regardless, the sensor is faulty.
4
If the sensor responds to the vacuum pump, the issue is in the vacuum source — check for a massive intake leak that is preventing the engine from building normal vacuum.
5
Inspect the signal wire for shorts to the 5V reference line or other voltage sources.
Estimated Repair Cost
$20 - $250
Parts + labor, varies by vehicle and location
The manifold absolute pressure sensor circuit is outputting a voltage above the maximum expected threshold. The PCM sees a reading that indicates an impossibly low vacuum (near or above atmospheric pressure) while the engine is running, which should not occur under normal conditions. This typically ...
The most common cause of P0108 (Manifold Absolute Pressure/Barometric Pressure Circuit High Input) is: Disconnected or leaking vacuum hose to the MAP sensor (sensor reads atmospheric)
Typical repair costs for P0108 range from $20 to $250, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The engine will run very rich because the PCM thinks the engine is under heavy load. This wastes fuel, fouls spark plugs, and can damage the catalytic converter. Not immediately dangerous but the vehicle should be repaired promptly. Avoid extended driving.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0108 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Fuel / Air Metering System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
