P0104: Mass or Volume Air Flow Circuit Intermittent

The mass air flow sensor measures how much air is entering the engine so the PCM can match fuel to it. That reading is central to fuel delivery, so the PCM watches the MAF circuit closely. P0104 is the 'circuit intermittent' member of the MAF family: the signal is present most of the time but momentarily glitches — dropping out, spiking, or going erratic — and then returns. That's distinct from the steady faults P0100 (general malfunction), P0102 (signal too low), and P0103 (signal too high). The intermittent nature is the whole story and it steers the diagnosis toward connections and contamination rather than a sensor that's simply dead.

The usual offenders are exactly what you'd expect from any intermittent circuit code. A loose or corroded MAF connector that makes and breaks contact, a chafed or cracked wire that opens only when it flexes or heats up, and electrical noise on the signal circuit all produce momentary dropouts. A dirty or contaminated MAF element — fouled by oil from an over-oiled aftermarket air filter or by dust from a poorly sealing filter — can give erratic readings that come and go with airflow. An unmetered air (vacuum) leak that opens and closes, a partially blocked or loose air intake duct, and a sensor beginning to fail round out the list. Because the fault often isn't present when you go looking, a static test frequently passes, which is the trademark frustration of intermittent codes.

For the driver, P0104 shows up as occasional hesitation, surging, a brief stumble or stall, an inconsistent idle, and a check engine light that may come and go. Performance and fuel economy can wander as the PCM reacts to the glitchy signal. The car is generally driveable between events. Catching it means chasing the fault while it's happening: freeze-frame data, a recorded live-data drive that reproduces the glitch, and a wiggle-test of the MAF connector and harness while watching the airflow reading. Cleaning a dirty MAF and inspecting the intake for leaks are cheap, high-yield first steps.