P0102 P0xxx · Powertrain (P) Medium severity
Mass Air Flow Circuit Low Input
The MAF signal stays below the plausible minimum. The ECU falls back to a speed-density calculation, which keeps the car drivable but with compromised mixture control.
Severity guidance: Medium — drivability or emissions affected, book it in this week
Symptoms you will notice
- Hard starting
- Stalling
- Limp mode
- Very poor fuel economy
Common causes
Ordered from most to least likely — start at the top.
- 1 Open signal wire or connector
- 2 Failed MAF sensor
- 3 Blown sensor supply fuse
- 4 Water ingress in the connector
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Check for 12 V supply and good earth at the sensor connector.
- ✓ Back-probe the signal wire; it should vary smoothly with throttle.
- ✓ Wiggle the harness while watching the PID to find an intermittent break.
- ✓ Compare MAF reading against the calculated load PID.
Repair options
- Replace the MAF sensor
- Repair the harness or connector
- Replace the supply fuse
P0102 — frequently asked questions
Will the car still run? +
Yes, in a fallback mode using RPM and throttle as a substitute — drivable but not right.
Is unplugging the MAF a valid test? +
It proves the ECU's fallback works, but it does not prove the sensor is good. Measure the signal instead.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.