Trouble codes › P0174
P0174 System Too Lean (Bank 2)
Fuel and air
P0174 means bank 2 is running lean (too much air or too little fuel), most often from a vacuum leak or a dirty MAF sensor.
The same as P0171, on bank 2 of a V6 or V8 (the side without cylinder 1). The engine computer is adding as much fuel as it's allowed on bank 2 and the mixture is still lean, so either unmeasured air is getting in or fuel delivery is short.
Usually drivable for now, but get it fixed soon. Stop if it starts misfiring or the check-engine light flashes.
Common causes
- A vacuum leak, especially on the bank 2 side of the intake
- A dirty or failing mass airflow (MAF) sensor
- Low fuel pressure or volume: pump, filter or regulator
- Clogged bank 2 injectors
- An exhaust leak before the bank 2 front oxygen sensor
Symptoms
- Check-engine light
- Rough idle, hesitation
- Sometimes misfires on bank 2
Common on: Ford F-150, Toyota Tacoma
What to check first
- If P0171 is set too, focus on causes that affect both banks: the MAF sensor, a large vacuum leak (intake boot, PCV) or fuel pressure.
- If only bank 2 is lean, look for a vacuum or exhaust leak on that side.
- Compare bank 1 and bank 2 long-term fuel trims with a scan tool at idle and at 2,500 rpm.
- Clean the MAF sensor with MAF cleaner and recheck; smoke-test the intake for leaks.
What does P0174 mean on your vehicle?
The likely cause depends on your engine. iRepair researches your exact year, make, model and engine (service bulletins, recalls and owner reports) and tells you what to check first. Your first 3 questions are free.
Ask iRepair about P0174No scanner? Most auto parts stores read check-engine codes for free.
Related codes
General guidance for P0174 on most vehicles. Some makers use the same code a little differently; confirm in the service information for your vehicle, put safety first, and see a professional when in doubt.