CodelampTwo codes together
P0101 and P0171 together: the airflow sensor and a lean mixture
P0101
- In plain words
- The airflow sensor's reading does not make sense for how the engine is running.
- Standard name
- Mass or Volume Air Flow Sensor "A" Circuit Range/Performance
- System
- Air intake and airflow sensing
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
P0101 says the mass airflow sensor's reading does not fit how the engine is running. P0171 says bank 1 is lean. A sensor that under-reads the air makes the computer add too little fuel, so the two often share one cause.
Likely causes, most common first
- A dirty mass airflow sensor. Dust or oil on its sensing wire makes it read low.
- A failing mass airflow sensor. Cleaning does not help a sensor that is wearing out.
- An air leak after the sensor. A cracked intake boot or loose clamp lets in air the sensor never measures, which can set both codes.
- A clogged air filter or a damaged sensor connector. Less common.
What you can note yourself
- Note whether the air filter was changed recently, and whether an oiled filter was fitted.
- Note any hesitation when you press the pedal.
What to tell the shop
- Both codes, and any recent air filter or intake work.
- Ask them to check for intake leaks after the sensor before replacing it.
This page gives no verdict on whether a car is safe to drive; a mechanic can.