CodelampCame back after a repair
P0171 came back after cleaning the airflow sensor
P0171
- In plain words
- The engine is getting too much air or too little fuel on bank 1.
- Standard name
- System Too Lean (Bank 1)
- System
- Fuel and air mixture
General information, not a mechanic's diagnosis: have a mechanic confirm before any repair.
What the computer saw
Cleaning the mass airflow sensor fixes a lean code only when dirt on the sensor was the cause. If P0171 is back, the cause is likely somewhere else, or the sensor itself is failing.
Likely causes, most common first
- A vacuum leak. The most common cause of a lean code, and cleaning a sensor does nothing for it.
- An air leak after the sensor. A cracked intake boot or a loose clamp, sometimes disturbed while the sensor was out.
- A failing airflow sensor. A worn sensor still reads low when clean.
- Low fuel pressure. A weak pump or clogged filter.
What you can note yourself
- Note how long the light stayed off after the cleaning.
- Note whether P0174 is now stored too.
What to tell the shop
- That the sensor was cleaned, when, and how long the code stayed away.
- Ask for a smoke test and a fuel pressure check.
This page gives no verdict on whether a car is safe to drive; a mechanic can.