Mass Air Flow Circuit Malfunction
What does P0100 mean?
The P0100 code means the vehicle's onboard diagnostic system has detected: Mass Air Flow Circuit Malfunction. This is a serious severity code.
Common Symptoms
- Check Engine Light on
- Engine stalls
- Hesitation on acceleration
- Rich or lean running
- Hard starting
Probable Causes (Ranked by Likelihood)
- Faulty MAF sensor Very High
- Wiring damage or poor connector at MAF High
- Air leak between MAF and throttle body Moderate
- Contaminated MAF sensing element Moderate
- PCM fault Low
Step-by-Step Diagnostic Procedure
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Check MAF sensor wiring and connector for corrosion, bent pins, or chafing.
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With engine running, monitor MAF g/s reading. At idle, a 4-cylinder should show 2-7 g/s. Erratic or zero readings indicate sensor failure.
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Clean the MAF sensor with dedicated MAF cleaner spray and retest.
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Check for air leaks in the intake boot between MAF and throttle body.
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Compare actual vs. calculated MAF with a scan tool at various throttle positions.
Frequently Asked Questions
Can I clean a MAF sensor instead of replacing it?
Yes, and it often works if contamination is the cause. Use only dedicated MAF cleaner. Do not touch the sensing wire and allow it to dry completely before reinstalling.
What happens if I drive with a bad MAF sensor?
The ECU will use a fallback fuel map, which causes poor fuel economy, rough running, and may damage the catalytic converter over time.