Fault codeP0102

MODERATE

Mass or Volume Air Flow Circuit low Input

What this code means

Mass or Volume Air Flow Circuit low Input.

P0102 is a generic code: it means the same thing on every make. P0102 belongs to family P01xx — Fuel and air metering. Its page explains how to read a code and groups all its codes by part.

Mass airflow sensor (airflow meter)

The airflow sensor sits in the intake duct between the air filter and the throttle. A heated wire or film measures how much air enters the engine, and the control unit uses it to calculate how much fuel to inject.

Symptoms

Hard starting, unstable idle, stalling, engine stumbling and short of power. The airflow sensor signal is so low that the control unit considers it impossible: silent sensor, missing supply or broken wire. The unit usually falls back to a default value, and the engine runs, but badly.

Common causes

Sensor connector unplugged, oxidised or with a pin pushed back
Wire cut or chafed in the loom, missing supply or ground
Sensor burnt out or heavily fouled
Large air leak after the sensor, starving it
Sensor supply circuit fuse

How to diagnose it

Start with the connector: unplug it, look at the pins, plug it back firmly. With a multimeter, check for supply (often 12 V or 5 V) and ground at the connector, ignition on. No supply, trace the loom back.

If the supply is there, watch the signal in live data: if it stays at zero with the engine running, the sensor is dead. Unplug it: if the engine runs better without it, the diagnosis is confirmed.

Watch it live in Klaro

With an OBD2 adapter plugged in, these live readings show the part at work, when your car reports them:

Mass air flow
Intake manifold pressure
Short term fuel trim bank 1
Long term fuel trim bank 1

What to do

Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.

Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →