What P0108 means
The manifold absolute pressure (MAP) sensor measures the pressure behind the throttle; on vehicles without a separate barometric sensor it also supplies the ambient pressure, read at key-on or wide-open throttle – hence 'MAP/BARO'.
How the engine computer detects it
It is a three-wire sensor with 5 V reference, ground and signal. P0108 means the signal voltage is above its upper limit – typically an open ground (low reference), a signal wire shorted to 5 V or battery voltage, or a failed sensor. Like P0107 it describes the voltage, not real overpressure; genuinely excessive boost is P0234. Documented limits: GM gasoline above 86 % of 5 V, GM diesel above 97 %, GM/Saab 2.0T above 4.80 V for 4 s, Ford above 4.88–4.96 V for 5 s. The engine substitutes a modelled value, which often makes the mixture too rich; turbo engines limit boost.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- Rich mixture, sooting, higher consumption
- Rough idle, loss of power or limp mode on turbo engines
Common causes
- Ground (low reference) wire open or connector corroded Most likely
- Signal wire shorted to 5 V or battery voltage Possible
- MAP sensor failed internally Possible
- Engine control module faulty Less likely
How to diagnose P0108
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: manifold absolute pressure sensor, sensor wiring, sensor reference voltage.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 1
- Fuel and air metering
- 08
- Specific fault
Questions drivers ask
Can I drive with code P0108?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P0108?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0108 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P0108 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.