How do I test a MAP sensor?

The quickest check needs no tools beyond a scan tool. Switch the ignition on but do not start the engine, then compare the MAP sensor's live reading with the barometric pressure reading. With the engine stopped the manifold is at atmospheric pressure, so the two should be within a couple of kPa of each other, around 101 kPa near sea level. If they disagree, the sensor is faulty. If they agree, start the engine and watch the value drop sharply at idle and rise as you blip the throttle.

Can a vacuum leak cause P0106?

Yes, and it is one of the most common causes. A leak raises the pressure in the inlet manifold above what the control unit expects for the throttle position it is commanding, so the sensor reports an accurate figure that fails the plausibility check. Perished vacuum hoses, a leaking intake manifold gasket and a stuck-open EGR valve all produce it.

Will P0106 fail an MOT?

Yes. The engine management lamp it lights is a major defect for petrol cars first used on or after 1 July 2003 and diesels from 1 July 2008, recorded 371,859 times in the DVSA data behind this site. Manifold pressure feeds both fuelling and ignition timing, so a car with this code also stands a good chance of failing the exhaust emissions limits.

Is a MAP sensor the same as a MAF sensor?

No, though they do a related job. A MAF sensor sits in the intake pipe and measures the mass of air flowing past it. A MAP sensor sits on or near the inlet manifold and measures the pressure inside it, from which the control unit calculates airflow. Some engines have one, some the other, and many modern engines have both and cross-check them, which is how plausibility codes like P0106 and P0101 get set in the first place.

Powertrain code · standard

P0106Manifold pressure sensor reading is not believable

Standard definition: Manifold Absolute Pressure Sensor Range/Performance

Last updated 27 July 2026

Quick answer

The manifold absolute pressure sensor is producing a signal in the right range, but one that does not fit what the engine is doing. It is a plausibility fault rather than a broken wire, and the cause is often the engine rather than the sensor.

How the car works this out

The MAP sensor measures absolute pressure in the inlet manifold, which falls well below atmospheric at idle and rises towards atmospheric — or above it on a turbocharged engine — at full throttle. The control unit compares that reading against throttle angle, engine speed, measured airflow and, on many cars, the barometric pressure sensor. P0106 is set when the comparison fails repeatedly. A useful quirk: with the ignition on and the engine stopped, the MAP sensor should read roughly the same as barometric pressure, around 101 kPa at sea level, and a sensor that does not is proven faulty before the engine is even started.

What you might notice

Rough or uneven idle
Hesitation, surging or poor throttle response
Heavier fuel consumption
Black smoke on a diesel, or a rich smell on a petrol
Harsh or oddly timed gearchanges on an automatic
Reduced power on turbocharged engines

What causes it

Most likely first. A code names the check that failed, not the part that failed it, so more than one of these can produce the same number.

1A blocked, split or disconnected vacuum hose to the sensor, on engines where it is mounted away from the manifoldCommon
How to check: Pull the hose off and check it is clear by blowing through it. Carbon and oil block the small port at the manifold end more often than the hose itself perishes.
2Carbon or oil fouling on the sensor element, which slows its response rather than stopping itCommon
How to check: Remove the sensor and look at the sensing port. Electrical contact cleaner on the element, left to dry fully, sometimes restores it.
3An intake or vacuum leak changing the actual manifold pressureCommon
How to check: A smoke test of the intake, which finds in minutes what an hour of listening for hisses will not.
4A sticking exhaust gas recirculation valve holding the manifold pressure upPossible
5A failed MAP sensorPossible
6Worn engine internals or badly out-of-spec valve timing, both of which reduce the vacuum the engine can pullLess common
How to check: A cylinder leakage or compression test. This is the uncommon answer, but it is the one that explains a P0106 that survives every other repair.

What to do about it

1Switch the ignition on without starting and compare the MAP reading against barometric pressure on a scan tool. They should be near identical; if they are not, the sensor is at fault and nothing else needs investigating.
2Check the vacuum hose and its port at the manifold if the sensor is remotely mounted. A blocked port is cheap, common and quick.
3Have the intake smoke tested for leaks before buying parts.
4Clean the sensor rather than replacing it as a first move, unless the key-on comparison has already condemned it.
5If the code persists with a new sensor, healthy hoses and no leaks, ask for compression figures. A tired engine cannot pull the vacuum the control unit expects.

Can you keep driving?

Briefly, gently

Driveable, but the fuelling and the ignition timing are both built on the manifold pressure figure, so the car will be rough and thirsty and may pull poorly. On a turbocharged engine the boost control also depends on it, and a car that cannot trust its own boost reading tends to fall into limp mode at the worst moment.

Will it fail an MOT?

An illuminated engine management lamp is a major defect on petrol cars first used from 1 July 2003 and diesels from 1 July 2008, and it accounts for 371,859 recorded failures. P0106 makes the emissions side of the test riskier than most sensor codes, because the manifold pressure figure drives fuelling and ignition timing together, so both the CO and hydrocarbon readings on a petrol and the smoke opacity on a diesel can shift out of limits.

The light this turns on

Engine management lightThe engine management system has found a fault it cannot correct and has stored a code for it. The car will usually still drive, but an illuminated engine light is an automatic MOT failure on petrol cars first used from 1 July 2003 and diesels from 1 July 2008.

Common questions

How do I test a MAP sensor?: The quickest check needs no tools beyond a scan tool. Switch the ignition on but do not start the engine, then compare the MAP sensor's live reading with the barometric pressure reading. With the engine stopped the manifold is at atmospheric pressure, so the two should be within a couple of kPa of each other, around 101 kPa near sea level. If they disagree, the sensor is faulty. If they agree, start the engine and watch the value drop sharply at idle and rise as you blip the throttle.
Can a vacuum leak cause P0106?: Yes, and it is one of the most common causes. A leak raises the pressure in the inlet manifold above what the control unit expects for the throttle position it is commanding, so the sensor reports an accurate figure that fails the plausibility check. Perished vacuum hoses, a leaking intake manifold gasket and a stuck-open EGR valve all produce it.
Will P0106 fail an MOT?: Yes. The engine management lamp it lights is a major defect for petrol cars first used on or after 1 July 2003 and diesels from 1 July 2008, recorded 371,859 times in the DVSA data behind this site. Manifold pressure feeds both fuelling and ignition timing, so a car with this code also stands a good chance of failing the exhaust emissions limits.
Is a MAP sensor the same as a MAF sensor?: No, though they do a related job. A MAF sensor sits in the intake pipe and measures the mass of air flowing past it. A MAP sensor sits on or near the inlet manifold and measures the pressure inside it, from which the control unit calculates airflow. Some engines have one, some the other, and many modern engines have both and cross-check them, which is how plausibility codes like P0106 and P0101 get set in the first place.

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