MAPSensor

Manifold Absolute Pressure Sensor (MAP)

Group: Air and fuel

The MAP sensor measures the pressure (or vacuum) inside the intake manifold. The computer uses it to estimate engine load and, on engines without a MAF, to calculate how much air is coming in. On turbo engines it also measures boost pressure.

Contents

What does the MAP sensor do?

When the throttle is almost closed, the pistons create vacuum in the manifold and the absolute pressure is low. At wide open throttle the pressure approaches atmospheric (or exceeds it on turbo engines). The MAP turns that pressure into a voltage. The computer uses it to calculate engine load, adjust injection and timing, and check that the EGR valve is working. With the ignition on and the engine off, the MAP also measures barometric pressure (altitude).

Where is it located?

On top of the intake manifold, or connected to it by a vacuum hose. Turbo engines usually have another sensor before the throttle body to read boost pressure.

Signal type and reference values

  • 3 wires: 5 V supply, ground and signal.
  • Ignition on, engine off, at sea level: 4.5 to 4.8 V (about 100 kPa).
  • Warm idle: 0.9 to 1.5 V (about 25 to 40 kPa).
  • Deceleration with the throttle closed: below the idle value.
  • Wide open throttle: close to 4.5 V on naturally aspirated engines.

Values are a guide only: always check the manufacturer's data for your engine.

Symptoms of a bad MAP sensor

  • Rough idle and bucking.
  • High fuel consumption and black smoke (rich mixture) or lack of power (lean mixture).
  • The engine stalls when you come to a stop.
  • Pinging when accelerating.
  • Codes P0105 to P0109, sometimes together with P0171 or P0172.

How to test the MAP sensor step by step

  1. Check the vacuum hose that feeds the sensor: it must be intact, free of oil and properly connected.
  2. Ignition on, engine off: compare the kPa reading with the barometric pressure for your altitude.
  3. Start the engine: at idle the pressure should drop to 25 to 40 kPa. If it does not drop, there is a big leak or the sensor is not responding.
  4. Check for 5 V supply and a good ground at the connector.
  5. Apply vacuum to the sensor with a hand vacuum pump and check that the voltage drops in proportion.

Trouble codes related to the MAP sensor

Frequently asked questions about the MAP sensor

What is the difference between the MAP and the MAF sensor?
The MAF measures the mass of air coming in. The MAP measures the pressure in the manifold. Some engines use only one, others use both: the MAF for fueling and the MAP to check load, EGR and boost.
Does altitude affect the MAP sensor?
Yes. At 2,500 meters (about 8,200 ft) barometric pressure is around 75 kPa, so every reading will be lower than at sea level. The computer takes this into account.

Updated September 25, 2026. Values are a guide only: always confirm them in the service manual for your engine.

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