P0108: MAP/Barometric Pressure Circuit High (Meaning, Causes, Fixes)
What P0108 means
The MAP sensor measures the pressure (vacuum) inside the intake manifold. Per RepairPal, the engine computer (PCM) uses it to control the air-fuel ratio, ignition timing and many emission controls. OBD-Codes.com explains that it's usually a three-wire sensor (a ground, a 5-volt reference from the PCM, and a signal wire back to the PCM) and that higher engine vacuum means a lower voltage. The two sources describe the trigger differently. OBD-Codes.com says P0108 sets if the PCM sees more than 5 volts from the MAP sensor, or a voltage higher than it considers normal for the conditions. RepairPal says it sets when the MAP/Baro signal stays above 4.5 volts for 10 seconds or more while the throttle position, RPM and oxygen sensor values are changing. Their typical voltage ranges also differ slightly: OBD-Codes.com says about 1 volt at idle to about 5 volts at wide-open throttle, while RepairPal says about 4 volts or more when accelerating to 1 volt or less when decelerating. Check the specs for your vehicle. Low engine vacuum also raises the signal, so OBD-Codes.com notes a worn engine can set this code even when the sensor is fine. Related MAP codes are P0105 (circuit), P0106 (range/performance), P0107 (circuit low) and P0109 (intermittent).
Severity: can I keep driving?
Drive with caution, fix soon
Get it checked soon. RepairPal rates P0108 'Urgent', and OBD-Codes.com says the engine may run poorly, may not run at all, and may blow black smoke. If the engine stalls, won't start or runs very rough, don't drive it (especially in traffic) until it's fixed.
Common symptoms
- Check engine light on (both sources)
- Engine runs poorly; RepairPal says noticeably poor performance in some cases
- Engine may not run at all (listed by OBD-Codes.com)
- Hard starting in some cases (listed by RepairPal)
- Lower fuel economy (both sources)
- Black smoke from the exhaust (listed by OBD-Codes.com)
Likely causes
Roughly most to least common, based on the sources below. Your vehicle may differ.
- Faulty MAP/barometric pressure sensor (both sources)
- Intake manifold vacuum leak (both sources)
- Leak in the vacuum supply line to the MAP sensor (listed by OBD-Codes.com)
- Faulty or corroded MAP sensor wiring or connections (RepairPal); OBD-Codes.com specifically lists a short on the signal wire, a short on the 5-volt reference wire, or an open in the ground circuit
- Worn engine making low vacuum (listed by OBD-Codes.com)
- Faulty PCM, rarely; OBD-Codes.com's test steps only point to it after the harness has been checked
Diagnostic steps you can do
Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.
- Read all stored codes and note the freeze frame data. Several 'high voltage' sensor codes at once can point to a shared wiring or reference-voltage problem rather than several bad sensors.
- Inspect the MAP sensor vacuum hose for cracks, a loose fit or damage, and look for intake vacuum leaks.
- Check the MAP sensor connector for corrosion, loose terminals and damaged wiring.
- With a scan tool and the key on and engine off, compare the MAP reading with the barometric (BARO) reading. OBD-Codes.com says they should match; if MAP is more than 0.5 volt off BARO, the sensor is the likely fault.
- Start the engine and watch the MAP reading at idle. OBD-Codes.com says about 1.5 volts is normal (it varies with altitude); if it's normal, the problem is likely intermittent, so check the hoses and wiggle-test the harness and connector.
- Clear the code and see if it returns before buying parts.
Typical fixes
- Repair intake or vacuum leaks, or replace a damaged MAP vacuum hose
- Clean or repair corroded connections, an open ground, or a short in the MAP sensor harness
- Replace the MAP sensor once vacuum, hose and wiring check out
- Repair a low-vacuum engine problem if the vacuum gauge shows less than about 15 to 16 in. Hg (per OBD-Codes.com)
- Repair a stuck-open EGR valve or faulty idle air control motor if that's the real cause (RepairPal lists both as reasons a MAP sensor gets replaced unnecessarily)
- Replace the PCM only if testing shows voltage on the MAP signal input with the sensor wire removed (OBD-Codes.com)
Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.
🛠 When to call a pro
- The engine stalls, won't start or runs very rough
- The scan tool shows more than 4.5 volts at idle; OBD-Codes.com's next step is checking actual engine vacuum with a vacuum gauge
- Tracing a short means unplugging the PCM connector and testing the signal wire, which is easy to get wrong
- RepairPal warns the MAP sensor is often replaced when the real cause is a vacuum leak, a stuck-open EGR valve or a bad idle air control motor
Where to buy
Plain search links. Always match parts to your exact year, make, model and engine.
FAQs
Does P0108 mean I need a new MAP sensor?
Not necessarily. Both sources list vacuum leaks and wiring problems as causes, OBD-Codes.com adds a worn engine with low vacuum, and RepairPal says the sensor is often replaced when the real problem is a vacuum leak, a stuck-open EGR valve or a bad idle air control motor.
What's the difference between P0107 and P0108?
Both are MAP sensor circuit codes. P0107 means the signal voltage is too low; P0108 means it's too high.
Is it safe to drive with P0108?
RepairPal rates it 'Urgent', and OBD-Codes.com says the engine may run poorly or not at all. Get it diagnosed soon, and don't drive if the engine is stalling or running very rough.
How much does it cost to fix P0108?
Neither source gives a repair cost. It depends on whether it's a hose, wiring, the sensor or an engine vacuum problem, so get a diagnosis and a written estimate first.
Sources
Last reviewed 2026-10-23. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.