P0174
System Too Lean (Bank 2)
What it means
Your engine's computer has detected that the air-fuel mixture in the second bank of cylinders (if your engine has two) is too lean, meaning there's too much air or not enough fuel for proper combustion.
Is it safe to drive?
Driving with a lean condition can lead to engine damage (overheating, misfires), catalytic converter damage, and reduced performance. It's best to diagnose and repair it promptly.
Most likely causes
Vacuum Leaks
highLeaks in vacuum lines, intake manifold gaskets, or PCV system can allow unmetered air into the engine, causing a lean condition, especially if localized to Bank 2.
Faulty Mass Air Flow (MAF) Sensor
mediumA dirty or failing MAF sensor can incorrectly report less air entering the engine than there actually is, leading the PCM to inject too little fuel for both banks.
Low Fuel Pressure or Clogged Fuel Injectors
mediumA weak fuel pump, clogged fuel filter, faulty fuel pressure regulator, or dirty/clogged fuel injectors can prevent adequate fuel delivery to Bank 2.
Exhaust Leak (before O2 sensor)
lowAn exhaust leak before the upstream oxygen sensor on Bank 2 can draw in outside air, causing the O2 sensor to read lean and the PCM to try to add more fuel, but the actual mixture is still lean.
Related help
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