Powertrain, generic · Fuel and air metering

P0102 Mass or Volume Air Flow Sensor A Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

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

Symptoms

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

Repair estimate

DifficultyEasyDIY possible
Parts and labour€20–300
Time0.3–1.5 h

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

What to check first

  1. Check connector pins
  2. Measure signal at idle
  3. Inspect intake for leaks

Parts involved

mass air flow sensormass air flow sensor wiringsensor supply voltage

Related codes

P0100P0101P0103P0104P010C

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