CodeXOBD

P0100 — Mass or Volume Air Flow Circuit Malfunction

P0100 means the module detected an electrical problem in the mass airflow sensor circuit — the signal is missing, out of range, or shorted. It is a circuit fault, not a reading problem.

Moderate

The engine will run on default fuel maps but may surge, hesitate, or idle roughly. Fuel economy will be noticeably worse. This code will cause an emissions test failure.

$10–$400Parts, typical range
0.3–1.5 hLabour
estimateNot a quote · 2026 basis

What P0100 means

P0100 is the circuit-level companion to P0101. Where P0101 means the sensor is reading implausibly, P0100 means the electrical signal itself is absent or outside the valid voltage range. The module checks for opens, shorts to ground, and shorts to power on the MAF signal wire. A missing or out-of-range signal forces the module into a default fueling strategy based on throttle position and engine speed alone.

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 P0100

Wiring or connector fault in the MAF circuit

Very likelylow costeasy

A broken wire, corroded connector, or poor ground in the MAF signal circuit produces a missing or out-of-range signal. This is more common than a failed sensor.

MAF sensor has failed internally

Likelymedium costeasy

The sensor's internal electronics have failed, producing no signal or a signal permanently out of range.

Moisture in the MAF sensor connector

Possiblelow costeasy

Water intrusion into the connector can short the signal or create intermittent connections. Common after pressure washing or heavy rain.

How to diagnose it

1

Inspect the MAF sensor connector

Disconnect and inspect the connector for corrosion, moisture, or damaged pins. Clean and re-seat, then clear the code.

Tools: Inspection lightIf it passes: Connector is clean and intact. Continue to step 2.If it fails: Clean or repair the connector, clear the code, and re-test.
2

Check for voltage at the sensor

With the ignition on, check for a 5V reference voltage at the sensor connector and a clean ground.

Tools: MultimeterExpected: 5V reference, near 0V groundIf it passes: Power and ground are correct. The sensor is the likely fault.If it fails: Trace the wiring back to the module for an open or short.
3

Test the sensor output

With the engine running, check the MAF signal voltage. At idle it should read approximately 0.5-1.0V and rise with engine speed.

Tools: Multimeter, OBD-II scanner with live dataExpected: 0.5-1.0V at idle, rising with RPMIf it passes: Sensor is producing a signal. The fault may be intermittent.If it fails: No signal or fixed voltage — replace the sensor.

Related codes

P0101P0102P0103

Common questions

What is the difference between P0100 and P0101?

P0100 is an electrical circuit fault — the signal is missing or out of valid range. P0101 means the signal is present but implausible for the current engine conditions, usually from a dirty sensor.

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.