Fuel and air code
P0108: Manifold pressure sensor signal too high
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $5 | $60 |
| Labor: 0.8 to 2.5 hours × $125 to $175 an hour | $100 | $438 |
| Fees: shop supplies, disposal, diagnostics | $0 | $25 |
| Total, rounded | $100 | $530 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in Boston, $31.54 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, vacuum leak repair. Which repair your car needs depends on a proper diagnosis.
The manifold pressure sensor reads the pressure inside the intake. This time it sent a very high value, one the engine could not actually be producing. The computer then assumes the engine is under heavy load and can send too much fuel, causing black smoke and a rich mix.
- Safe to drive?
- Usually yes, for now
- Most common cause
- Failed MAP sensor
Short drives are okay, but the car may run rich or stumble.
What you may notice
- Rough idle
- Black smoke from the tailpipe
- Poor fuel economy
- Hesitation when accelerating
Common causes, most likely first
- Failed MAP sensor
- Shorted wiring
- Bad connector
- Blocked vacuum line
- Computer fault (rare)
Check this first
Check the sensor plug for a loose fit or green corrosion, and look at the vacuum hose to the sensor for a pinch or blockage. If your sensor is mounted directly on the intake, check that the seal is intact.
Other repairs that sometimes fix P0108
| Repair | Typical range, Boston |
|---|---|
| Diagnostic scan (check engine light) | $60 to $290 |
| CAN bus wiring repair | $190 to $1,275 |
| ECU / engine control module replacement | $430 to $2,350 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Massachusetts rules require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
P0108 questions
Can a fuel problem look like this?
No, but the sensor's wrong reading can make the car run rich as a side effect. That is why a high-pressure reading can feel like a fuel problem even though the fuel system itself is fine.
Do I need a new sensor?
Often yes, but the wiring should be tested first. A shorted or damaged wire can send a high signal from a good sensor, so the shop should check the circuit before ordering a new part.
Is it safe to drive?
Short trips are generally okay, but you may notice poor mileage and smoke, and a long-term rich mix can damage the catalytic converter. Do not leave it for months.
How much does it cost to fix P0108?
The most common fix, vacuum leak repair, has a typical range of $100 to $530 in Boston. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Related codes
- P0106: Manifold pressure sensor reading doesn't match
- P0107: Manifold pressure sensor reads low
- P0101: Air flow sensor reading seems off
- P0172: Engine getting too much fuel (bank 1)
More fuel and air codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.