Symptoms of a faulty MAP sensor can include: Malfunction Indicator Light (MIL) illumination Lean or rich air-fuel mixture Failed emissions test Poor fuel economy 1. Malfunction Indicator Light (MIL) Illumination A faulty MAP sensor may not provide accurate manifold pressure data instantaneously, or may provide incomprehensible data to the ECM. Shop for New Auto Parts at 1AAuto.com this video to learn all about Manifold Absolute Pressure (MAP) sensors, and how Symptoms Of A Bad MAP Sensor 1. Check Engine Light. The engine control unit constantly monitors all the sensors in your car engine while you drive 2. Lean Air-fuel Mixture. The MAP sensor's primary purpose is to measure the air pressure in the intake manifold to 3. Rich Air-fuel Mixture. The Here are the most common symptoms of a bad manifold absolute pressure sensor: Due to erroneous engine load calculation, a defective MAP sensor will impair the ECM's ability to regulate air/fuel ratio and ignition timing. This can result in an overly rich or underly rich air-fuel combination. A bad MAP sensor might cause the following symptoms: qCmIRq.