OBD-II · Engine and powertrain (P)
P0102
Mass air flow circuit low input
What it means
The MAF signal voltage or frequency is below the circuit threshold; check the electrical circuit before diagnosing air-flow restrictions (P0101).
Symptoms
- hesitation or flat spots when accelerating
- reduced power, sometimes limp mode
- rough idle or stalling
- black smoke on diesels
- engine warning light
Likely causes, most likely first
| No. | Cause |
|---|---|
| 01 | unplugged MAF connector |
| 02 | open signal wire |
| 03 | signal short to ground |
| 04 | low sensor supply voltage |
| 05 | failed MAF sensor electronics |
What to check, step by step
- 01Inspect the MAF connector and wiring for damage, corrosion or a loose plug
- 02Check the sensor supply and ground with a meter
- 03Read the MAF value in live data: with the key on and engine off it should be near zero, and it should rise smoothly with rpm
- 04Unplug the MAF with the engine idling: if the engine runs better unplugged, the sensor is suspect
- 05Replace the sensor with an OE-quality part if the wiring is good (cheap copies often read wrong)