Honda Civic P0171
TL;DR
P0171 (Honda Civic) = System Too Lean, Bank 1. Severity: medium. Top Civic-specific causes: dirty MAF sensor (40%), cracked PCV/intake hose (25%), weak fuel pump or clogged injectors (20%), vacuum leak (15%). Typical fix: $20 (clean MAF) to $600 (fuel pump at a shop).
Why P0171 is common on the Honda Civic
Honda's K-series and L-series engines run a returnless fuel system and rely heavily on a clean mass-air-flow signal. On higher-mileage Civics (notably 2006–2015), the most frequent triggers for P0171 are MAF contamination from oiled aftermarket filters and brittle PCV/intake hoses that crack and admit unmetered air.
What to check first
- Clean the MAF sensor with MAF-safe cleaner and recheck fuel trims.
- Inspect the PCV hose and intake boot for cracks; smoke-test for vacuum leaks.
- Check long-term fuel trim at idle vs. 2,500 rpm — a leak that improves with rpm points to a vacuum source.
Summary
| Code | P0171 |
|---|---|
| Meaning | System Too Lean (Bank 1) |
| Severity | Medium |
| Can I drive? | Yes, with caution |
| Top cause | Dirty MAF sensor |
| Typical cost | $20–$600 |
Full diagnostics
For the complete step-by-step diagnostic and repair guide, see P0171 — full diagnostics.
Frequently asked questions
Can I drive my Civic with a P0171 code?
Usually yes, short-term. The car may idle rough or hesitate, but the main risk is that a prolonged lean condition can cause misfires and damage the catalytic converter, so repair it within a week or two.
How much does it cost to fix P0171 on a Honda Civic?
From about $20 if cleaning the MAF sensor solves it, up to roughly $400–$600 if a failing fuel pump or injectors must be replaced at a shop.
What is the most common cause of P0171 on a Civic?
A dirty or failing mass-air-flow (MAF) sensor, closely followed by a cracked PCV or intake hose letting in unmetered air.