Codes P0105 through P0109 indicate Manifold Absolute Pressure (MAP) sensor faults. The MAP sensor measures the pressure inside the intake manifold and is used by the ECM to calculate engine load and air mass on speed-density fuelling systems. When the MAP sensor fails, drivability problems are immediate and obvious.
What the MAP Sensor Does
The MAP sensor is a pressure transducer mounted on or near the intake manifold. It measures the absolute pressure (vacuum, in normal operation) inside the manifold. Higher engine load means less manifold vacuum (closer to atmospheric pressure); idle means strong vacuum (low absolute pressure). Combined with engine RPM, the ECM uses MAP to calculate how much air is entering the cylinders, then determines correct fuel injection quantity. Some vehicles use only MAP (speed-density), others combine MAF and MAP for more accurate measurements.
Common MAP Codes
P0105 is MAP circuit malfunction (general). P0106 is MAP circuit range/performance (sensor reading is implausible for engine operating condition). P0107 is MAP circuit low input (likely failed sensor or shorted signal). P0108 is MAP circuit high input. P0109 is MAP circuit intermittent. The codes often appear with running issues – lean codes (P0171), rich codes (P0172), or misfire codes (P0300 series) – because incorrect MAP readings cause the ECM to deliver wrong fuel mixture.
Symptoms
Rough idle that may improve at higher RPM (or vice versa). Hesitation under acceleration. Black smoke from the exhaust (rich condition). Surging at constant throttle. Stalling at idle or after coming to a stop. Poor fuel economy. Hard starting (especially when warm). Failed emissions tests on fuel-trim measurements.
Diagnosis
Start with a visual inspection. The MAP sensor is typically mounted on or near the intake manifold, sometimes connected by a vacuum hose (older designs) or directly threaded into the manifold (modern designs). Check the vacuum hose for cracks, leaks, or oil contamination. Check the electrical connector for corrosion or loose pins.
With a scan tool, watch the MAP live data. At idle with engine warm, MAP should typically read 25 to 35 kPa (about 7 to 10 inches Hg of vacuum). At wide-open throttle (or with the engine off and key on), MAP should read close to atmospheric pressure – about 100 kPa at sea level (lower at altitude). A sensor that does not change with RPM and load, or shows the same value with engine off as at idle, has failed.
Vacuum Leak Confusion
A common cause of MAP-related symptoms is not a failed sensor but a vacuum leak. The MAP reads correctly but the leak introduces unmetered air, throwing off fuel calculations. Inspect all vacuum hoses, intake gaskets, and PCV system components before replacing the MAP sensor. Smoke testing the intake reveals leaks quickly.
Cleaning vs Replacing
Like MAF sensors, MAP sensors can sometimes be cleaned if oil contamination from PCV blow-by has fouled the sensing element. Use MAF sensor cleaner spray (not brake cleaner). However, MAP sensors are usually more robust than MAF sensors and cleaning is less commonly effective. Replacement is usually the cure if there is a confirmed sensor fault. Quality aftermarket sensors (Bosch, Delphi, Standard Motor Products) are usually fine.
MAP specifications and locations are vehicle-specific. MechanicMate offers PDF workshop manuals for over 960 models at mechanicmate.net/shop.
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