Fuel and air

P029E — Cylinder 2 Fuel Trim at Maximum Limit

Severity: medium Drive with care, to a shop

What P029E means

The engine control unit constantly adjusts how much fuel each injector delivers to keep the air-fuel mixture near ideal. P029E means the correction for cylinder 2 has hit its maximum limit and the computer can't compensate any further. The mixture in that cylinder is usually too lean or too rich because of an air leak, a bad injector, or a fuel delivery problem.

Symptoms

  • Check Engine light on
  • Rough or unstable idle
  • Weak acceleration and loss of power
  • Poor fuel economy
  • Misfires, possibly with related codes
  • Higher exhaust emissions

Possible causes

  1. Vacuum or intake leak near cylinder 2 (hoses, manifold gasket)
  2. Clogged, leaking or failing cylinder 2 fuel injector
  3. Faulty oxygen sensor giving wrong mixture data
  4. Failing MAF or MAP sensor
  5. Low fuel pressure from a weak pump, clogged filter or bad regulator
  6. Damaged injector wiring or connector
  7. Exhaust leak ahead of the oxygen sensor

How to diagnose

  1. Read all codes and freeze frame data, and note any misfire codes
  2. Watch short-term and long-term fuel trims at idle and around 2,500 rpm
  3. Inspect intake ducts and vacuum hoses, and smoke test or spray-test for leaks
  4. Check the cylinder 2 injector connector and wiring, and measure injector resistance
  5. Swap the injector with a neighbor to see whether the problem follows it
  6. Measure fuel pressure and whether it holds after shutoff
  7. Check MAF, MAP and oxygen sensor readings
  8. Inspect the exhaust for leaks

Common fixes

  • Repair vacuum leaks and replace damaged hoses or the intake manifold gasket
  • Clean or replace the cylinder 2 injector
  • Replace a faulty MAF, MAP or oxygen sensor
  • Replace the fuel filter, pump or pressure regulator if pressure is low
  • Repair injector wiring or connector

Questions and answers

What does P029E mean?

The engine computer can't correct the air-fuel mixture in cylinder 2 any further because the trim has reached its limit. Common causes are an air leak, a bad injector or a fuel supply problem.

Can I drive with P029E?

Briefly and carefully, yes, but find the cause soon. Running with a wrong mixture for long can cause misfires and damage the catalytic converter.

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.