P029B
Cylinder 1 - Fuel Trim at Min Limit
Fuel & air metering
Generic OBD-II
High
What it means
P029B means the ECM has cut fuel to cylinder 1 as far as it can — its fuel trim has hit the minimum limit — and the cylinder is still running rich. In other words the computer is subtracting all the fuel it's allowed to and can't lean it out any further. A leaking injector or high fuel pressure is the usual cause; the engine idles rough but still runs.
High
Can I keep driving? Usually drivable but rough — cylinder 1 is running rich enough that the ECM has cut its fuel to the minimum. Fix it to avoid fouling and converter damage.
Common symptoms
What you'll notice
- Check-engine light on
- Rough idle
- Fuel smell or black smoke
- Reduced fuel economy
Common causes
Most likely first
- Leaking or over-delivering injector on cylinder 1Likely
- High fuel pressure (faulty regulator)Common
- Contaminated or over-rich fuelCommon
- Faulty oxygen/air-fuel sensor skewing trim on that bankLess often
- MAF sensor reading highLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check fuel-trim values to confirm cylinder 1 is being pulled toward the minimum.
- Inspect the cylinder 1 injector for leaking or over-delivery; test and compare with the others.
- Check fuel pressure against spec and test the pressure regulator.
- Inspect the oxygen/air-fuel sensor and MAF readings for skew.
- Correct the rich source, clear the code, and re-test fuel trims.
FAQ
Quick answers
Is it safe to drive with P029B?+
Short-term, yes, but a persistently rich cylinder can foul the plug and overheat the catalytic converter. Get the rich condition fixed soon.
Can I just clear P029B?+
It returns once the ECM again hits its minimum fuel limit for cylinder 1. The underlying rich condition must be corrected.
Related codes
Often seen with P029B
Read & clear P029B 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