Fuel and air

P029F — Cylinder 2 Fuel Trim at Minimum Limit

Severity: medium Drive with care, to a shop

What P029F means

P029F means the engine control module has reduced fuel to cylinder 2 as far as it is allowed to. This usually happens because that cylinder is running too rich and the ECM cannot lean it out any further. Individual cylinder trims are estimated from crankshaft speed variations and oxygen sensor data. Exact code wording can vary by manufacturer, so confirm with live data.

Symptoms

  • Check Engine light on
  • Rough idle
  • Higher fuel consumption
  • Reduced power or sluggish acceleration
  • Fuel smell or black smoke from the exhaust
  • Misfire in cylinder 2

Possible causes

  1. Leaking or stuck-open fuel injector on cylinder 2
  2. Injector electrical fault: open circuit, corroded connector, damaged wiring
  3. Fuel pressure too high (regulator or return line problem)
  4. Faulty oxygen, mass airflow (MAF) or manifold pressure (MAP) sensor
  5. Worn spark plug or weak ignition coil on cylinder 2 skewing the mixture estimate
  6. Mechanical cylinder issue such as low compression
  7. Software or ECM fault (rare)

How to diagnose

  1. Scan all codes and freeze frame data, noting any misfire or other fuel trim codes
  2. Review short and long term fuel trims and per-cylinder adjustments in live data
  3. Inspect the cylinder 2 injector connector and wiring for corrosion, chafing and poor contact
  4. Test injector resistance and the ECM control signal with a scope or noid light
  5. Measure fuel pressure and check the regulator against the manufacturer spec
  6. Inspect the cylinder 2 plug and coil, swapping with a neighbor cylinder if needed
  7. Check MAF, MAP and oxygen sensor readings for plausibility
  8. Run an injector balance or leak-down test, and a compression test if needed

Common fixes

  • Replace or professionally clean the cylinder 2 injector
  • Repair the injector wiring or connector
  • Replace the fuel pressure regulator or fix the cause of high pressure
  • Replace the faulty sensor (oxygen, MAF or MAP)
  • Replace the spark plug or coil, and apply an ECM software update if a bulletin exists

Questions and answers

What does P029F mean?

The ECM has cut fuel to cylinder 2 to its minimum allowed level because the mixture there is too rich. The most common culprit is that cylinder's fuel injector.

Can I drive with P029F?

Short trips to a shop are usually fine if the engine is not shaking badly and the check engine light is not flashing. Prolonged driving on a rich mixture can damage the catalytic converter and thin out the oil.

How do I find the cause of P029F quickly?

Look at per-cylinder trims and inspect the injector connector first. Then check fuel pressure and swap injectors or coils between cylinders to see whether the problem follows the part.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.