CodeXOBD

P0102 — Mass or Volume Air Flow Circuit Low Input

P0102 means the MAF sensor is reporting a voltage lower than the module considers possible. A disconnected sensor, a short to ground, or a failed sensor are the usual causes.

Moderate

The engine runs rich on default maps, with poor economy and possible black smoke from the exhaust. This code will cause an emissions test failure.

$10–$400Parts, typical range
0.3–1 hLabour
estimateNot a quote · 2026 basis

What P0102 means

P0102 sets when the MAF sensor signal voltage drops below the calibrated minimum, typically around 0.2V. This can mean the sensor is disconnected, the signal wire is shorted to ground, or the sensor itself has failed and is producing a permanently low output. The module falls back on default fueling, which is rich enough to protect the engine but too imprecise for normal operation.

Technical summary
SystemPowertrain — fuel and air metering
How the fuel mixture is decidedAir passes the mass airflow sensor, then the throttle, into the intake manifold and the cylinder. The module injects fuel to match the measured air, and the upstream oxygen sensor reports the result so it can correct itself. Air entering after the sensor was never measured, which is why a leak downstream of it makes the mixture run lean.Air inAirflow sensormeasures massThrottleCylinderfuel added hereO₂ sensorreports resultAny air entering after the sensor is fuel the module never accounted for

Symptoms you may notice

What causes P0102

MAF sensor disconnected or connector loose

Very likelylow costeasy

The most common cause — the sensor plug has worked loose or was left disconnected after service.

MAF signal wire shorted to ground

Likelylow costeasy

Chafed insulation on the signal wire can contact the engine or chassis ground, pulling the voltage to zero.

MAF sensor internal failure

Possiblemedium costeasy

The sensor's internal circuitry has failed, producing a permanently low or zero output.

How to diagnose it

1

Check that the sensor is connected

Visually verify the MAF sensor connector is fully seated and the latch is engaged.

If it passes: Connector is secure. Continue to step 2.If it fails: Reconnect, clear the code, and re-test.
2

Measure the signal voltage

With the ignition on and engine off, measure the MAF signal voltage. It should be around 0.2-0.5V with no airflow. If it is near 0V, the wire is shorted to ground or the sensor is dead.

Tools: MultimeterExpected: 0.2-0.5V at key-on, engine offIf it passes: Voltage is in range. The fault may be intermittent.If it fails: Voltage is near zero — check for a short to ground, or replace the sensor.
3

Inspect the MAF sensor wiring harness

Trace the MAF sensor wiring from the connector to the module. Look for chafed insulation, pinched wires, or corroded terminals that could cause a short to ground.

Tools: Inspection light, MultimeterIf it passes: Wiring is intact. The sensor is confirmed faulty.If it fails: Repair the damaged section of wiring.

Related codes

P0100P0101P0103

Common questions

Is P0102 serious?

It will not damage the engine, but the module is running on default fueling, which means poor economy and possible rich-running symptoms until it is fixed.

Last verified 2026-07-27 · Sources: SAE J2012 — Diagnostic Trouble Code Definitions and Failure Type Byte (SAE International)

This information is for general guidance and is not a substitute for professional diagnosis. Cost figures are estimates, not quotes.