P1201
Alternative Fuel Gas Mass Sensor Circuit Range Performance
What it means
P1201. Alternative Fuel Gas Mass Sensor Circuit Range Performance. This Chevy-enhanced code applies to Silverado, Sierra, Express, Savana Bi-Fuel.
Findings, check these first
- Faulty alternative-fuel gas mass sensor on CNG or bi-fuel conversions
- Chafed gas mass sensor harness near the alternative-fuel rail
- Corroded connector at the gas mass sensor from underhood moisture
- PCM alternative-fuel calibration mismatch after a component swap
Standard procedure
- Verify the vehicle alternative-fuel system type and conversion integrity first
- Backprobe the gas mass sensor signal and compare against spec on a Tech2 or GDS2
- Inspect the sensor harness routing for chafing near the fuel rail
- Check for PCM calibration updates covering the alternative-fuel system
- Replace the gas mass sensor only on confirmed out-of-range readings
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Sources and review
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Last updated 2026-09-19.
Report a correction for P1201. Include your vehicle, the issue and a source if you have one.