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DTC codes / P02xx · Fuel and air metering (injector circuits) / P029F

P029FCylinder 2 - Fuel Trim at Min Limit

P029F means the engine computer has detected that the fuel trim for cylinder 2 has reached its minimum limit, meaning the powertrain control module can no longer remove enough fuel to correct a rich condition on that specific cylinder. The computer monitors crankshaft speed fluctuations and adjusts individual cylinder fuel delivery, and when the correction hits the bottom of its allowed range, this code is stored.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or misfire-like shudder that may be intermittent
  • Slightly reduced fuel economy over time
  • Black soot on the tailpipe or spark plug for cylinder 2
  • Engine may stumble or hesitate under light acceleration
  • Strong fuel odor from the exhaust in severe cases

Common causes, most likely first

  1. Leaking or stuck-open fuel injector for cylinder 2
  2. Faulty spark plug or ignition coil causing incomplete combustion on cylinder 2
  3. Contaminated or restricted engine oil affecting variable valve timing on that cylinder
  4. Intake or exhaust valve sealing problem on cylinder 2
  5. Wiring or connector issue to the cylinder 2 injector or ignition coil
  6. Mechanical fault such as low compression on cylinder 2
  7. Engine computer software calibration issue or faulty powertrain control module

How to diagnose and fix it

  1. Scan all stored and pending codes, then record freeze-frame data to see when the fault occurs
  2. Inspect the spark plug and ignition coil for cylinder 2 for fouling, wear, or damage
  3. Check the fuel injector for cylinder 2 for leaks or incorrect spray pattern, swapping it with a known-good injector if possible
  4. Perform a compression test and cylinder leak-down test on cylinder 2 to rule out mechanical problems
  5. Check the wiring harness and connectors at the cylinder 2 injector and coil for corrosion or damage
  6. Verify fuel pressure and check for a leaking fuel pressure regulator or evap purge valve sticking open
  7. If all mechanical and electrical checks pass, reflash or replace the powertrain control module as a last resort

Why cylinder 2 fuel trim bottoms out

  • A rich condition on only one cylinder is almost never caused by a bad oxygen sensor, so avoid replacing sensors before checking injectors and ignition components.
  • A misfire on cylinder 2 can cause unburned fuel to enter the exhaust, which the oxygen sensor reads as rich and drives fuel trim to its minimum limit, so always diagnose misfires first.
  • Leaking injectors often test fine on a basic resistance check but still drip fuel; a professional injector flow test or swap is needed to confirm.
  • Carbon buildup on intake valves can absorb fuel and cause uneven running that mimics a rich trim on one cylinder, especially on direct-injection engines.
  • The code can set intermittently due to a poor electrical connection at the injector that only acts up when hot or vibrating.

Can I keep driving with P029F?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing because continued rich operation can damage the catalytic converter and waste fuel. If the check engine light flashes or the engine runs very rough, stop driving and have it towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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