P0174
System Too Lean (Bank 2)
medium
i Description
The engine is running too lean on Bank 2 (the cylinder bank that does not contain cylinder 1). Same root causes as P0171, but isolated to the other bank. If both P0171 and P0174 are present, the cause is likely common to both banks (MAF, fuel pressure).
? Common Causes
- Vacuum leak on Bank 2 side
- Dirty or faulty MAF sensor
- Low fuel pressure
- Exhaust leak on Bank 2
- Faulty Bank 2 O2 sensor
! Symptoms
- Check engine light
- Rough idle
- Hesitation
- Poor fuel economy
# Diagnostic Steps
- Same as P0171 but focus on Bank 2 side
- If P0171 is also present, focus on common causes (MAF, fuel pressure)
- Smoke-test intake for leaks on Bank 2 side
- Check Bank 2 upstream O2 sensor
⚙ Typical Fix
Same approach as P0171 — find and fix the lean cause on Bank 2.
Parts Needed
Varies based on root cause
Estimated Cost
$100-$500
↔ Related Codes
Q Frequently Asked Questions
Same as P0171 — short-term driving is OK, but address promptly to avoid engine and catalyst damage.
☞ Learn More
- What is OBD-II? — Complete guide to your car's diagnostic system
- How to Read DTC Codes — Step-by-step with a Bluetooth scanner
- OBD-II Scanner Buying Guide — Find the best scanner for your car