P0104 Mass air flow (MAF) sensor: signal drops out at times ("A")

By: Diagno editorial team · Updated: 2026-10-15

P0104 means: Mass air flow (MAF) sensor: signal drops out at times ("A"). The mass air flow (MAF) sensor measures how much air goes into the engine. Drive gently and have the car checked soon. The repair usually costs about €60–300 in Estonia. The most common cause: connector loose, damp or corroded.

What it means

The mass air flow (MAF) sensor measures how much air goes into the engine. The computer uses it to work out how much fuel to add. The signal drops out now and then. The most common cause is a loose connector or a chafed wire.

What you may notice

• Engine light on
• Less power
• Rough idle
• The engine may stall

What could be wrong

1. 1Connector loose, damp or corroded
2. 2Wire broken or chafed
3. 3Faulty MAF sensor
4. 4Engine computer fault (rare)

Repair difficulty: Easy

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? Check the air filter and its housing. Make sure the intake hose after the sensor is intact and the clamps are tight. You can do the simpler checks yourself.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the MAF sensor

Standard SAE description: Mass or Volume Air Flow "A" Circuit Intermittent