MAP Sensor for Mercedes Benz a-Class W168 W169 W176 M166 M266 OM651

A faulty MAP sensor typically triggers codes P0105 to P0109. P0105 indicates a circuit malfunction, P0106 indicates the signal is out of range, P0107 and P0108 indicate the signal is too low or too high respectively, and P0109 indicates an intermittent circuit fault. These codes combined with symptoms such as poor idle and black smoke are strong indicators of MAP sensor failure.

With an OBD2 scanner in live data mode, the MAP sensor should read close to atmospheric pressure (around 101 kPa) with the engine off, and drop to 30 to 50 kPa at idle with the engine running due to manifold vacuum. Under wide open throttle the reading should rise back toward atmospheric. A sensor that reads flat or does not respond to throttle changes has failed. You can also test supply voltage and signal output with a multimeter.

You can drive short distances but engine performance will be noticeably degraded. The ECU uses the MAP sensor to calculate fuel delivery - a faulty sensor causes incorrect fuelling which leads to poor economy, rough running, and increased emissions. On turbocharged engines a faulty MAP sensor can also prevent boost control from operating correctly. Replace it as soon as possible to avoid further damage.

The Manifold Absolute Pressure (MAP) sensor measures intake manifold pressure to help the ECU calculate the correct fuel and ignition timing. It is critical for engine efficiency, particularly on turbocharged and supercharged vehicles.

Symptoms include poor acceleration, rough idle, excessive fuel consumption, black smoke, engine hesitation, and a Check Engine light with codes P0105-P0109. Turbocharged vehicles may also experience boost control issues.

A MAF (Mass Air Flow) sensor directly measures the mass of air entering the engine. A MAP sensor measures manifold pressure and the ECU calculates air mass from that reading. Many vehicles use one or the other; some use both. They are not interchangeable.