Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.

P0104: Mass or volume airflow “A” circuit intermittent/erratic

The airflow signal is dropping out, spiking or becoming implausibly unstable instead of staying consistently low or high.

What P0104 means

The airflow signal is dropping out, spiking or becoming implausibly unstable instead of staying consistently low or high. Intermittent faults often require logging or reproduction before the cause can be confirmed.

Can I still drive?

Treat unpredictable stalling or hesitation more seriously than a warning-light-only fault. A brief, gentle journey may be reasonable while the vehicle behaves normally and the lamp is steady amber. Stop and arrange recovery if symptoms recur in traffic, during acceleration or whenever safe control is in doubt.

Symptoms

• Intermittent hesitation, jerking or loss of power.
• Fluctuating idle or occasional stalling.
• Engine-management light that appears and disappears.
• Variable fuel economy.
• A fault that may be difficult to reproduce in the workshop.

Common causes

• Loose connector terminals or corrosion.
• Wire broken inside its insulation or harness chafing that reacts to vibration.
• Intermittent sensor failure or contamination.
• Split or moving intake duct.
• Unstable sensor power supply or earth.
• Less commonly, ECU or software issues after circuit and intake faults are excluded.

Safe first checks

• Record when the fault occurs, including engine temperature, rain, bumps, acceleration and engine speed, and preserve freeze-frame data. With the ignition off, inspect the connector lock, visible terminals, loom supports and intake hose. Do not perform a hands-on wiggle test near belts, fans or hot components with the engine running.

Typical UK fix cost

Estimated diagnostic charge: £75–£180, as reproducing and logging an intermittent fault may take longer. Estimated total for a connector, local wiring, intake or MAF repair: £150–£750. Elusive loom or ECU faults can exceed £800–£1,500+. These are broad estimates, not quotations.

Related models

This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.

Related fault codes

• P0102: Mass or volume airflow “A” circuit low input
• P0103: Mass or volume airflow “A” circuit high input
• P0110: Intake-air temperature sensor 1 circuit
• P0111: Intake-air temperature sensor 1 circuit range/performance

Sources

• DG Technologies — P0104 definition and code-diagnosis context
• DENSO — MAF operating principles and fault symptoms
• Start Rescue — UK complex-diagnostic price context

A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.