Fuel and air

P02A3 — Cylinder 3 Fuel Trim at Minimum Limit

Severity: medium Drive with care, to a shop

What P02A3 means

The engine computer continuously adjusts fuel for each cylinder using oxygen sensor data and crankshaft speed variations. P02A3 means the correction for cylinder 3 has hit its minimum limit: the ECU is already removing as much fuel as it can, yet that cylinder still runs richer than it should. Exact code wording can vary slightly between manufacturers.

Symptoms

  • Check Engine light on
  • Rough idle or hesitation
  • Higher fuel consumption
  • Fuel smell or black smoke from the exhaust
  • Sluggish acceleration
  • Hard starting or stalling when warm

Possible causes

  1. Leaking or stuck-open fuel injector on cylinder 3
  2. Fuel pressure too high (regulator or return line problem)
  3. Worn spark plug or weak ignition coil on cylinder 3
  4. Skewed readings from an oxygen, MAF or MAP sensor
  5. Damaged injector wiring or connector
  6. Mechanical problem in the cylinder (low compression, valve)
  7. Oil diluted by fuel

How to diagnose

  1. Read all codes and freeze frame data and look for other mixture or misfire codes
  2. View short and long term fuel trims and any per-cylinder corrections on a scan tool
  3. Inspect the cylinder 3 injector connector and wiring
  4. Check the plug and coil on cylinder 3, then swap them with a neighbor to see if the fault follows
  5. Measure fuel pressure and compare it with the spec
  6. Test injector resistance and leak-down, or bench test it if needed
  7. Check oxygen and MAF/MAP sensor readings for plausibility
  8. Run a compression test on cylinder 3 and check the oil level and smell

Common fixes

  • Replace or professionally clean a leaking injector
  • Replace the spark plug or ignition coil on cylinder 3
  • Replace the fuel pressure regulator or fix the cause of high pressure
  • Replace a faulty oxygen, MAF or MAP sensor
  • Repair the injector harness or connector
  • Change the oil if it is diluted with fuel

Questions and answers

What does P02A3 mean?

The ECU cannot lean out cylinder 3 any further because its fuel correction is at the minimum limit. That cylinder is usually getting too much fuel, most often from the injector.

Can I drive with P02A3?

Briefly, yes, but get it checked soon. A rich mixture raises fuel use, thins the oil and can damage the catalytic converter.

Should I replace the injector right away?

No. Check the plug, coil, fuel pressure and wiring first, and replace the injector only once it is confirmed faulty.

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.