P0104 — Intermittent problem with mass airflow sensor circuit

The code indicates the car’s mass airflow sensor signal is cutting in and out. This sensor measures the air entering the engine to help control fuel delivery. An intermittent circuit means the sensor’s electrical connection or wiring is unstable, causing inconsistent readings. It can cause rough running, poor fuel economy, or stalling.

Common causes

The cause is almost always one of a few things. Here they are — P0104 rarely comes from anything outside this list:

• Loose or corroded electrical connector at the MAF sensor
• Damaged or frayed wiring harness near the sensor
• Faulty mass airflow sensor
• Contaminated or dirty MAF sensor element
• Intermittent ECU or sensor internal fault

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Inspect and clean MAF sensor connector and terminals
2. Check wiring harness for damage or loose connections
3. Clean the MAF sensor with proper cleaner
4. Replace the mass airflow sensor if faults persist
5. Scan and clear codes, test drive to confirm repair

That is what holds for P0104 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.