Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval.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

P0102: Mass or volume airflow “A” circuit low input

The ECU is seeing an airflow-sensor signal below its expected electrical or frequency threshold.

What P0102 means

The ECU is seeing an airflow-sensor signal below its expected electrical or frequency threshold. “Low input” describes the signal level; it does not necessarily mean that too little air is physically entering the engine.

Can I still drive?

Have the fault checked promptly because poor acceleration or stalling can become a traffic hazard. A short, gentle trip may be reasonable only if the warning is steady amber and operation is otherwise normal. Stop and arrange assistance if the vehicle hesitates severely, stalls or loses enough power to make driving unsafe.

Symptoms

• Engine-management light.
• Rough idle or stalling.
• Difficult starting.
• Hesitation, poor acceleration or reduced-power mode.
• Increased fuel consumption.
• Occasional backfiring on some vehicles.

Common causes

• Unplugged or incompletely latched connector.
• Open signal wire, short to earth, missing supply or poor earth.
• Corroded, wet, loose or backed-out terminal.
• Internally failed or contaminated sensor.
• Intake restriction, leak or abnormal actual airflow on systems whose monitoring strategy can detect it.

Safe first checks

• Switch the ignition off. Check that the plug is locked, accessible terminals look straight and dry, and the visible loom is not trapped, melted or chafed. Inspect the filter, airbox and intake duct. If the code appeared immediately after air-filter or under-bonnet work, recheck anything that was disturbed. Supply, earth and signal tests should use the correct wiring diagram and suitable equipment.

Typical UK fix cost

Estimated diagnostic charge: £60–£130. Estimated total for a connector, local wiring, intake or MAF-sensor repair: £120–£650. Long harness faults or ECU involvement can cost £800–£1,500+. Treat these as broad planning figures only.

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

• P0100: Mass or volume airflow “A” circuit malfunction
• P0101: Mass or volume airflow “A” circuit range/performance
• P0103: Mass or volume airflow “A” circuit high input
• P0104: Mass or volume airflow “A” circuit intermittent/erratic

Sources

• DG Technologies — P0102 definition and diagnostic-code limitations
• DENSO — MAF construction, signal use and fault symptoms
• Start Rescue — UK diagnostic pricing and sources of variation

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.