P02A6
Cylinder 4 - Fuel Trim at Max Limit
Fuel & air metering
Generic OBD-II
High
What it means
P02A6 means the engine controller has had to add the maximum amount of fuel it can to cylinder 4 to keep it running correctly — its fuel trim has hit the limit. That means cylinder 4 is running lean, usually from an air leak, a restricted injector, or low fuel pressure. The engine idles rough and can hesitate until the underlying lean cause is fixed.
High
Can I keep driving? You can usually drive, but cylinder 4 is running lean and rough. Sustained lean misfire can harm the catalytic converter, so fix it soon.
Common symptoms
What you'll notice
- Check-engine light on
- Rough idle or a miss from one cylinder
- Hesitation and reduced power
- Slightly poorer fuel economy
Common causes
Most likely first
- Vacuum or intake leak affecting cylinder 4Likely
- Clogged or weak fuel injector on cylinder 4Common
- Low fuel pressure limiting deliveryCommon
- Exhaust leak upstream of the oxygen sensor skewing trimLess often
- Low compression on cylinder 4Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the max fuel trim is specific to cylinder 4.
- Inspect for vacuum and intake leaks near cylinder 4; smoke-test if needed.
- Check fuel pressure and the cylinder 4 injector's flow (clean or replace if restricted).
- Look for exhaust leaks ahead of the oxygen sensor.
- If fueling and air are good, compression-test cylinder 4. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P02A6?+
For short trips, but a lean, misfiring cylinder runs rough and can damage the catalytic converter over time. Have it fixed promptly.
Can I just clear P02A6?+
It will return until the lean condition on cylinder 4 — usually a leak or a fuel-delivery issue — is corrected.
Related codes
Often seen with P02A6
Read & clear P02A6 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