What Does P0100 Mean?
The PCM has detected a general malfunction in the mass air flow (MAF) sensor 'A' circuit. This could be a complete circuit failure, no signal, or a signal that is electrically invalid. The MAF sensor is critical for calculating the correct air-fuel mixture. The driver will likely notice poor drivability including rough idle, hesitation, stalling, poor fuel economy, and the MIL will be illuminated.
Common Causes
30%
Faulty mass air flow sensor (internal circuit failure)
25%
Damaged, corroded, or disconnected MAF sensor connector
20%
Open or shorted wiring in the MAF sensor circuit
15%
Blown fuse or loss of power supply to the MAF sensor
10%
PCM internal driver circuit failure for the MAF input
Diagnostic Steps
1
Check the MAF sensor PID in live data — a stuck value of 0 g/s or an implausible fixed value indicates a circuit failure rather than a sensor accuracy issue.
2
Inspect the MAF sensor connector for bent pins, corrosion, moisture, or being unplugged; re-seat and test again.
3
With the key on engine off, verify power and ground at the MAF sensor connector — typically 12V battery voltage on the power pin and <0.1V on the ground pin.
4
Back-probe the MAF signal wire and check for voltage change as the engine runs — the signal should vary between approximately 0.5V at idle and 4.5V at WOT; a flat or absent signal confirms a circuit issue.
5
Check the MAF sensor fuse in the underhood fuse box — a blown fuse will kill the sensor entirely; investigate what caused the fuse to blow before replacing.
Estimated Repair Cost
$50 - $350
Parts + labor, varies by vehicle and location
The PCM has detected a general malfunction in the mass air flow (MAF) sensor 'A' circuit. This could be a complete circuit failure, no signal, or a signal that is electrically invalid. The MAF sensor is critical for calculating the correct air-fuel mixture. The driver will likely notice poor drivabi...
The most common cause of P0100 (Mass or Volume Air Flow "A" Circuit Malfunction) is: Faulty mass air flow sensor (internal circuit failure)
Typical repair costs for P0100 range from $50 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle may be drivable but with significantly degraded performance. The PCM will use a default airflow calculation based on TPS and RPM, which is less accurate. Stalling is possible, especially at idle. Drive cautiously to a repair facility; avoid highway driving if the engine stalls or hesitates badly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0100 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel / Air Metering System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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