What does MAP sensor low input mean?

It means the sensor's signal voltage has fallen below the minimum the engine control unit treats as physically possible, usually under about 0.2 volts. Since even a hard-idling engine cannot pull the manifold down that far, the control unit knows the reading is false rather than extreme. The cause is normally a broken or earthed signal wire, a missing five-volt reference supply, or a sensor that has failed short.

Why would the five-volt supply to a sensor be missing?

On most engines that reference voltage is shared between several sensors — manifold pressure, throttle position, fuel rail pressure and others. If any one of them fails with an internal short, it pulls the shared supply down and every sensor on it reports a low input at once. That is why a car with P0107 often has two or three other low input codes stored alongside it, and why unplugging sensors one at a time until the voltage returns is the fastest way to find the culprit.

Will P0107 fail an MOT?

Yes. The engine management lamp it lights is a major defect for petrol cars first used from 1 July 2003 and diesels from 1 July 2008, and 371,859 failures have been recorded against that defect. The car may also fail the emissions element, both because the fuelling is being calculated from a substitute value and because an engine in limp mode may not hold the steady fast idle the emissions reading requires.

Can I still start the car with P0107?

Usually, yes. The control unit falls back on a default manifold pressure figure so the engine will start and run, but expect long cranking, a poor idle and very little power. Some cars go into a fixed limp mode until the fault is repaired and the code cleared.

Powertrain code · standard

P0107Manifold pressure sensor reading too low

Standard definition: Manifold Absolute Pressure Sensor Low Input

Last updated 27 July 2026

Quick answer

The manifold pressure sensor signal has dropped below the lowest value the engine control unit accepts, which no running engine can actually produce. It points at a broken circuit or a dead sensor rather than a real pressure.

How the car works this out

The MAP sensor's output rises with absolute pressure, so even at hard idle with the throttle shut the signal never falls to the bottom of its range, and with the ignition on and the engine off it should sit near atmospheric. P0107 is set when the voltage falls below that floor, typically under about 0.2 volts. Because the reading is impossible rather than merely wrong, the fault is almost always in the wiring or the sensor: a signal wire earthed, a missing five-volt supply, or a sensor that has failed short.

What you might notice

Hard starting or extended cranking
Rough idle and stalling
Very poor power, sometimes with a persistent limp mode
Heavy fuel consumption
Black smoke from a diesel

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.

1The five-volt reference supply to the sensor missing, often because another sensor on the same shared supply has failed shortCommon
How to check: Measure the reference voltage at the MAP connector with the ignition on. If it is absent, unplug other sensors sharing that supply one at a time until it returns — the one that restores it is the failed sensor.
2The signal wire broken or shorted to earthCommon
3A corroded or water-filled connectorPossible
How to check: Unplug and inspect for moisture and green deposits, particularly on sensors mounted low or near the scuttle drain.
4A failed MAP sensorPossible
5On remotely mounted sensors, a hose left off after other work so the sensor sees a pressure it should notLess common

What to do about it

1Check the connector first, then the five-volt reference at the sensor. That single measurement splits the problem cleanly into a wiring fault or a sensor fault.
2If the reference voltage is missing, do not simply replace the MAP sensor. That supply is shared with several sensors on most engines, and one of the others may be dragging it down.
3Look for chafed wiring where the loom passes the engine or the bulkhead, especially if the fault is intermittent and comes and goes with engine movement.
4Confirm the repair with live data: with the ignition on and engine off the reading should sit at roughly atmospheric pressure, and it should drop sharply once the engine idles.

Can you keep driving?

Only to a garage

With no usable manifold pressure figure the control unit is guessing at both fuelling and timing, so many cars will start but run badly and some will drop straight into limp mode. It is not dangerous, but it is not a code to drive around on, and a diesel producing black smoke while it does so is loading up its particulate filter.

Will it fail an MOT?

The lamp alone is a major defect, one of 371,859 recorded failures against an illuminated engine malfunction indicator lamp. P0107 also puts the emissions check at risk twice over: the mixture is being calculated from a substituted value, and on many cars the car will not hold the steady fast idle the tester needs for the emissions readings. Repair it first, then allow a drive cycle before the test so the readiness monitors have completed.

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

What does MAP sensor low input mean?: It means the sensor's signal voltage has fallen below the minimum the engine control unit treats as physically possible, usually under about 0.2 volts. Since even a hard-idling engine cannot pull the manifold down that far, the control unit knows the reading is false rather than extreme. The cause is normally a broken or earthed signal wire, a missing five-volt reference supply, or a sensor that has failed short.
Why would the five-volt supply to a sensor be missing?: On most engines that reference voltage is shared between several sensors — manifold pressure, throttle position, fuel rail pressure and others. If any one of them fails with an internal short, it pulls the shared supply down and every sensor on it reports a low input at once. That is why a car with P0107 often has two or three other low input codes stored alongside it, and why unplugging sensors one at a time until the voltage returns is the fastest way to find the culprit.
Will P0107 fail an MOT?: Yes. The engine management lamp it lights is a major defect for petrol cars first used from 1 July 2003 and diesels from 1 July 2008, and 371,859 failures have been recorded against that defect. The car may also fail the emissions element, both because the fuelling is being calculated from a substitute value and because an engine in limp mode may not hold the steady fast idle the emissions reading requires.
Can I still start the car with P0107?: Usually, yes. The control unit falls back on a default manifold pressure figure so the engine will start and run, but expect long cranking, a poor idle and very little power. Some cars go into a fixed limp mode until the fault is repaired and the code cleared.

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