P0108: Manifold Absolute Pressure/Barometric Pressure Circuit High
The MAP sensor voltage is stuck too high, so the computer thinks the intake has almost no vacuum, as if the throttle were wide open.
What P0108 means
With P0108, the MAP signal has stayed above roughly 4.5 volts for 10 seconds or more while other sensors show the engine is not under full load, according to RepairPal. The computer reads that as almost no vacuum, so it calculates heavy load and adds fuel and adjusts timing. The cause can be electrical, like a signal wire shorted to voltage or a broken ground, or real, like a vacuum leak, a disconnected hose or an EGR valve stuck open that lets exhaust into the intake. A tired engine with low vacuum from worn valves or a timing problem can do it too. Shops compare the MAP reading to a mechanical vacuum gauge. If the gauge shows good vacuum but the sensor says otherwise, they test the wiring and sensor. If the gauge also shows low vacuum, they look for leaks or engine problems. RepairPal notes that MAP sensors are often replaced when the real fault is a leak or EGR valve.
Common symptoms
- Check engine light on
- Hard starting
- Poor gas mileage
- Rich running or black smoke
- Rough idle or weak performance
Most common causes
- Faulty MAP sensor
- Vacuum leak or disconnected MAP vacuum hose
- Signal wire shorted to voltage
- Open ground circuit at the sensor
- EGR valve stuck open
- Mechanical issue causing low engine vacuum
What to check yourself first
Check that the MAP sensor vacuum hose, if used, is connected and not cracked. Inspect the connector and wiring. A vacuum gauge on the intake should read roughly 17 to 21 inches at a warm idle on a healthy engine; much lower points to a mechanical or leak problem.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace MAP sensor | $201-$242 | When the sensor reads high with good wiring and normal vacuum. |
| Smoke test for intake leaks | $61-$90 | Rules out a vacuum leak, a cause RepairPal says often gets missed. |
| Replace EGR valve | $489-$632 | If the EGR valve is stuck open. |
| Electrical diagnosis to find a wiring or connector fault | $122-$179 | For an open ground or short to voltage. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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