P0171 on a Honda Civic
P0171 means system Too Lean (Bank 1). On the Civic, a few causes come up far more than others.
What P0171 usually means on a Civic
P0171 tells you the Civic is running lean - the ECU is adding fuel to compensate for extra air or missing fuel. On the 1.5T it is frequently a PCV or intake-boot leak, while on older cars a tired MAF reading or vacuum leak is typical. It often pairs with a rough cold idle. Long-term fuel trims climbing well into the double digits confirm the lean condition.
Most common causes on the Civic
- Vacuum or PCV leak
Cracked PCV hoses and brittle vacuum lines are the leading lean cause on higher-mileage Civics.
- Dirty or aging MAF sensor
A contaminated mass-airflow sensor under-reports air and drives trims lean.
- Intake or charge-pipe leak (1.5T)
A loose intercooler pipe or split boot lets metered air escape after the sensor.
- Weak fuel delivery
A failing fuel pump or clogged filter starves the engine under load.
What P0171 costs to fix on a Civic
Most Civic lean codes are cured cheaply - a can of MAF cleaner or a thirty-dollar PCV/vacuum hose - but a smoke test to find the leak is the smart first spend. A MAF sensor is a moderate part cost and a five-minute swap. Fuel-pump-related lean faults are the pricier outlier.
Year, engine and mileage change the answer. Start a case and Redline weighs these causes against what your car shows, then names the check that would settle it.
Other codes on the Honda Civic
Related symptoms
Honda Civic problems & recalls by year
Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0171 behavior is covered on the main P0171 page. Confirm with a scan tool before buying parts.
P0171 on your Civic?
Every problem becomes a Case. Tell Redline what your Civic is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.