P0108 means the engine control module has detected the manifold absolute pressure (MAP) sensor’s circuit voltage reading consistently too high — a distinctly electrical fault, different from our P0106 (MAP/barometric pressure range/performance) guide, which covers a case where the sensor’s readings are electrically valid but don’t make logical sense given other engine conditions. Because P0108 is a straightforward high-voltage electrical fault, wiring and the sensor’s connector are the first place to look, rather than the broader logic-based causes relevant to a range/performance code.
What Does P0108 Mean?
The MAP sensor measures pressure inside the intake manifold, which the engine control module uses to calculate how much air is entering the engine and, in turn, how much fuel to deliver. P0108 fires when the sensor’s output voltage reads persistently too high — a genuine electrical fault, distinct from P0106, which is stored when the sensor’s readings are electrically plausible on their own but don’t logically match what other sensors (like throttle position or RPM) suggest should be happening. This distinction matters diagnostically: P0108 points first at wiring, connectors, or the sensor itself, while P0106 points more toward vacuum leaks or genuine mechanical issues affecting actual manifold pressure.
Common Symptoms
- Check engine light on
- Rough idle or hesitation, since incorrect MAP data affects how much fuel the engine delivers
- Reduced fuel economy
- Possible hard starting
Common Causes, Most Likely First
- A short to a power source somewhere in the MAP sensor’s wiring, the most direct explanation for a persistently high voltage reading.
- A damaged or corroded connector at the MAP sensor itself.
- A failing MAP sensor with an internal fault causing it to output an incorrect high voltage regardless of actual manifold pressure.
- A disconnected or damaged vacuum line to the sensor on designs that use one, though this is somewhat less common as a cause of specifically a “high input” electrical fault.
How to Diagnose It
- Inspect the MAP sensor’s wiring and connector for visible damage or corrosion.
- Test the sensor’s output voltage with a multimeter, both with the key on/engine off and with the engine running, comparing against the manufacturer’s specification.
- Check for a short to power along the wiring harness if the sensor itself tests within range but the fault persists.
- Compare with P0106 if you’re trying to determine which MAP sensor guide applies — P0108 is specifically an electrical high-voltage fault.
Never work under a vehicle supported only by a jack. Use axle stands on firm, level ground, chock the wheels that stay down, and leave the car in gear or Park with the handbrake on. A jack lifts; stands hold.
Possible Fixes
| Cause | Fix | Typical cost |
|---|---|---|
| Wiring short to power | Repair the wiring | $100 – $250 |
| Damaged/corroded connector | Clean or replace the connector | $50 – $150 |
| Failing MAP sensor | Replace the sensor | $80 – $200 |
Can I Keep Driving With This?
Yes, in most cases, though address it reasonably soon — incorrect MAP sensor data affects the fuel mixture the engine control module calculates, which can cause a rough idle or reduced fuel economy the longer it’s left unaddressed.
When to See a Mechanic
Not urgent — check the sensor’s wiring and connector yourself first if comfortable doing so. More in our trouble codes section.
Frequently Asked Questions
What does P0108 mean?
It means the MAP sensor’s circuit voltage is reading consistently too high — a straightforward electrical fault, distinct from P0106’s more nuanced logic-based range/performance check.
Is P0108 the same as P0106?
No — P0106 means the sensor’s readings are electrically valid but don’t logically match other engine data, while P0108 means there’s a genuine electrical fault causing an abnormally high voltage reading.
What’s the most common cause of P0108?
A short to a power source somewhere in the MAP sensor’s wiring is the most direct and common cause of a persistently high voltage reading.
Is it safe to drive with a P0108 code?
Yes, in most cases, though address it reasonably soon since incorrect MAP data affects the fuel mixture calculation and can cause rough idle or reduced economy.
How much does it cost to fix P0108?
Often $100–$250 for a wiring repair, or $80–$200 if the MAP sensor itself needs replacement.
