P2179
System Too Lean Off Idle Bank 2
Fuel & air metering
Generic OBD-II
Medium
What it means
P2179 means that just off idle the engine's bank 2 air-fuel mixture is running too lean — too much air for the fuel being delivered. The ECM adds fuel to compensate, and when it can't keep up it sets this code. The most common causes are unmetered air from a vacuum or intake leak, an under-reading MAF sensor, or a fuel-delivery shortfall, rather than a fault that would stop the engine starting.
Medium
Can I keep driving? Driveable, but a lean mixture off-idle causes hesitation and can misfire; prolonged running lean risks engine and converter damage, so fix it soon.
Common symptoms
What you'll notice
- Check-engine light on
- Hesitation or stumble just off idle
- Rough idle and possible surging
- Reduced power; occasional lean misfire
- May enter a reduced-power/failsafe mode
Common causes
Most likely first
- Intake or vacuum leak on bank 2 (most common)Likely
- Faulty or contaminated MAF sensor under-reading airflowCommon
- Low fuel pressure or restricted fuel deliveryCommon
- Weak or dirty fuel injectors on bank 2Less often
- Incorrectly routed or leaking PCV hoseLess often
- Faulty upstream (front) O2 sensor or an exhaust leak near it skewing readingsLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame and fuel-trim data, then smoke-test the intake for vacuum leaks on bank 2 — the usual cause.
- Inspect and clean the MAF sensor and check the air filter and intake ducting.
- Check fuel pressure and injector operation on bank 2.
- Verify PCV routing and inspect for exhaust leaks near the front O2 sensor; replace the O2 sensor only if data confirms it.
FAQ
Quick answers
Is it safe to drive with P2179?+
For short trips, yes, but a persistent lean condition can cause misfires and overheat the catalytic converter over time, so don't put off the repair.
Can I just clear P2179?+
It returns once fuel trims run lean again. The underlying air leak, fuel-delivery, or sensor issue has to be corrected first.
Related codes
Often seen with P2179
Read & clear P2179 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX