P0102: Mass or Volume Air Flow Sensor A Circuit Low

What does P0102 mean?

The mass air flow sensor (MAF) sits between the air filter and the throttle or compressor and measures how much air the engine draws in; fuel quantity, load and ignition are calculated from it. Most are hot-film or hot-wire sensors that output either a voltage or, on GM, Saab and newer Ford systems, a frequency. P0102 means the signal is below its electrical lower limit – a frequency that is too low or a voltage that is too low. Documented limits: GM petrol 450 Hz or less, GM diesel below 276 Hz, Ford digital below 1.5 kHz for 5 s, Ford analogue below 0.244 V. 'Low' describes the signal: typically an open or grounded signal wire, missing supply voltage or failed electronics. Saab notes that a large leak between sensor and throttle can also cause it. GM and Saab need two trips; the engine runs on a calculated substitute value.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Lack of power, hesitation, substitute value mode
• Rough idle or stalling
• Higher fuel consumption

Common causes

• High Signal wire open or shorted to ground, connector corroded or loose
• High Sensor electronics failed
• Medium Missing supply voltage (fuse, relay) or poor ground
• Low Large leak or disconnected duct between sensor and throttle

Likelihood is a general estimate across vehicles; your make and model may differ.