P1171
Fuel System Lean During Acceleration
What it means
P1171. Fuel System Lean During Acceleration. This Chevy-enhanced code applies to Silverado, Sierra, Tahoe, Suburban, Avalanche.
Findings, check these first
- Weak fuel pump unable to hold pressure under load
- Clogged fuel filter restricting flow on acceleration
- Vacuum leak opening under engine torque
- Dirty MAF sensor under-reporting airflow
- Exhaust leak ahead of the upstream O2 sensor
Standard procedure
- Log fuel pressure under acceleration with a gauge and a Tech2 or GDS2
- Check long-term fuel trims at idle versus load to isolate vacuum versus fuel delivery
- Clean and test the MAF sensor before replacing it
- Smoke-test the intake and brake booster hose for leaks
- Replace the fuel pump or filter only on failed pressure tests, then verify trims recover
Look up another code
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Sources and review
Review: checked against the recorded source material.
- OBDII Code P1171 CHEVROLET - Fuel System Lean During Acceleration | Engine-Codes.com
archived reference page (engine-codes.com via Wayback Machine)
Supports: code identity and Chevrolet application
Fetched directly. Exact title match. Model and year fitment remain curator claims.
Last updated 2026-09-13.
Report a correction for P1171. Include your vehicle, the issue and a source if you have one.