Powertrain, generic · Fuel and air metering

P0108 Manifold Absolute Pressure/Barometric Pressure Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

The manifold absolute pressure (MAP) sensor measures the pressure behind the throttle; on vehicles without a separate barometric sensor it also supplies the ambient pressure, read at key-on or wide-open throttle – hence 'MAP/BARO'. It is a three-wire sensor with 5 V reference, ground and signal. P0108 means the signal voltage is above its upper limit – typically an open ground (low reference), a signal wire shorted to 5 V or battery voltage, or a failed sensor. Like P0107 it describes the voltage, not real overpressure; genuinely excessive boost is P0234. Documented limits: GM petrol above 86 % of 5 V, GM diesel above 97 %, GM/Saab 2.0T above 4.80 V for 4 s, Ford above 4.88–4.96 V for 5 s. The engine substitutes a modelled value, which often makes the mixture too rich; turbo engines limit boost.

Likely causes

Ground (low reference) wire open or connector corroded
Signal wire shorted to 5 V or battery voltage
MAP sensor failed internally
Engine control module faulty

Symptoms

  • Check engine light on
  • Rich mixture, sooting, higher consumption
  • Rough idle, loss of power or limp mode on turbo engines

Repair estimate

DifficultyEasyDIY possible
Parts and labour€20–200
Time0.3–1 h

Typical range across vehicles; the real cost depends on what the testing finds.

What to check first

  1. Check the vacuum hose to the sensor
  2. Check ground circuit
  3. Compare reading with a vacuum gauge

Parts involved

manifold absolute pressure sensorsensor wiringsensor reference voltage

Related codes

P0105P0106P0107P0109P0238P0234

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, newtonnet.co.uk.