P029A
Cylinder 1 - Fuel Trim at Max Limit
Fuel & air metering
Generic OBD-II
High
What it means
P029A means the fuel trim for cylinder 1 has reached its maximum correction limit — the module is adding as much fuel as it can, yet the cylinder still reads lean. This usually points to a vacuum leak, a weak or clogged injector, or low fuel supply on that cylinder, and it can lead to rough running or a misfire if left unaddressed.
High
Can I keep driving? The engine can still run but cylinder 1 is running lean with fuel correction maxed out — expect rough running and possible misfire, so fix it before it worsens.
Common symptoms
What you'll notice
- Check-engine light on
- Rough idle or a misfire on cylinder 1
- Hesitation or reduced power
- Hard starting or increased fuel consumption
Common causes
Most likely first
- Vacuum or intake leak affecting cylinder 1Likely
- Clogged or weak fuel injector on cylinder 1Common
- Low fuel pressure or restricted fuel supplyCommon
- Faulty upstream air/fuel or oxygen sensor skewing trimLess often
- MAF/MAP metering error or an ignition misfire on that cylinderLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check live fuel-trim values to confirm cylinder 1 is running lean.
- Inspect for vacuum and intake leaks near cylinder 1 first — the cheapest common cause.
- Test the cylinder-1 injector for clogging or weak flow and compare with the others.
- Verify fuel pressure and check the MAF and upstream oxygen/air-fuel sensor readings.
- Repair the leak, injector, or sensor identified, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P029A?+
Short trips are usually fine, but a lean cylinder can misfire and, over time, damage the catalytic converter. Have it diagnosed soon.
Can I just clear P029A?+
It returns once fuel trim hits its limit again. The underlying lean condition on cylinder 1 must be corrected.
Related codes
Often seen with P029A
Read & clear P029A 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