P0108 code: Manifold Absolute Pressure (MAP) Sensor Circuit High
P0108 means manifold Absolute Pressure (MAP) Sensor Circuit High. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0108 means
The manifold absolute pressure (MAP) sensor reports intake-manifold pressure so the computer can set fuel and timing for the current load. P0108 means the MAP signal is reading too high. A very common and cheap cause is a disconnected, cracked, or leaking vacuum hose to the sensor — the sensor then sees near-atmospheric pressure all the time. A failed sensor or a wiring fault can also cause it. Check the vacuum line first; it's often the culprit.
P0108 symptoms
- Rough idle, hesitation, or poor acceleration
- Engine running rich (black smoke, fuel smell)
- Reduced fuel economy
- Hard starting in some cases
- Check-engine light
What it costs to fix P0108
Typical range: $20–$300 · about ~0.2–1 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Vacuum hose repair/reconnect | $5–$30 | ~0.2–0.5 hrs |
| MAP sensor | $30–$120 | ~0.3–0.8 hrs |
| Wiring / connector repair | $10–$120 | ~0.5–1.5 hrs |
Check the vacuum hose first — a disconnected or cracked line is a frequent and nearly free cause of a high MAP reading. If that's good, the sensor itself is inexpensive.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0108 for my exact vehicle →
How to fix P0108
Easy — basic tools, most owners can do this
- Find the MAP sensor's vacuum feed and check it
If your MAP sensor connects to the manifold through a hose, follow it end to end: off its nipple, split at a bend, collapsed, or plugged with oily sludge all leave the sensor seeing near-atmospheric pressure. Direct-mount sensors need their seal and port checked instead. It is the cheapest cause and a very common one.
- Compare the engine-off and idle readings
With the key on and engine off, the MAP value should match barometric pressure. Start the engine: at warm idle it should fall well below that and rise instantly with a throttle blip. A reading that stays parked at atmospheric points back at the vacuum feed; one pinned at the top of its scale points at the circuit.
- Back-probe the reference, ground, and signal wires
Most MAP sensors are three-wire: a 5-volt reference, a ground, and a signal. With the key on, confirm the reference is close to 5 volts and the ground drop is minimal. A signal reading almost the full 5 volts usually means an open sensor ground or a signal wire shorted to the reference — a wiring fault rather than a sensor.
- Jumper the signal to ground as a circuit check
Unplug the sensor and, using a fused jumper, briefly connect the harness signal terminal to ground while watching the scan tool. The reading should drop to its minimum. If it does, the wiring and computer can see the circuit and the fault is the sensor or its ground; if nothing moves, the signal wire or computer is the problem.
- Bench-check with a vacuum pump, then replace
Apply vacuum to the sensor's port with a hand pump while monitoring its signal: the reading should fall smoothly as vacuum rises and recover when you release it. A sensor that holds a high reading regardless has failed internally. Replacement is usually one or two fasteners and a plug; clear the code and recheck the idle reading afterward.
DIY or shop? Few codes reward a home mechanic as quickly as P0108: a split hose, a popped-off line, or a failed sensor bolted on top of the manifold covers most cases, and the voltage checks need only a basic meter. A shop makes sense if the 5-volt reference is shared with other sensors and something on that circuit is dragging it around, or if the signal wire is shorted inside a harness you can't easily reach. Fix it promptly — a MAP reading stuck high makes the computer think the engine is under heavy load and fuel it rich.
Tools for the DIY steps: Scan tool with live data · Digital multimeter · Hand vacuum pump with gauge · Fused jumper wire · Replacement vacuum hose
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0108.
Start a case with P0108 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0108?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0108: common questions
Can I drive with P0108?
Redline can't make a driving call from this code alone. Expect rough running and possibly a rich-running engine; get it diagnosed promptly and fix it before an emissions test. If the engine stalls or the check-engine light starts flashing, stop driving.
What usually causes P0108?
A disconnected, cracked, or leaking vacuum hose to the MAP sensor is a very common and cheap cause — the sensor then reads atmospheric pressure constantly. Check that line first before suspecting the sensor or wiring.
Is P0108 the sensor or a hose?
Often the hose — a quick, nearly free fix. If the vacuum line is intact, then the sensor or wiring is the next suspect. Checking the hose first can save you a sensor you didn't need.
How much does it cost to fix P0108?
Frequently almost nothing if it's the vacuum hose. A replacement MAP sensor is still inexpensive, and wiring repairs are modest. Start with the cheap, common cause.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0108 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0108 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.