Fuel and air

P02CD — Cylinder 1 Fuel Injector Offset Learning at Limit

Severity: medium Drive with care, to a shop

What P02CD means

The engine control module continuously trims each injector so fuel delivery stays balanced between cylinders. P02CD means the learned correction for cylinder 1 has hit its maximum allowed limit, so the module can't compensate any further. This usually means the injector is not delivering the amount of fuel it is commanded to.

Symptoms

  • Check engine light on
  • Rough idle, especially at low rpm
  • Misfire on cylinder 1
  • Reduced power and sluggish acceleration
  • Higher fuel consumption
  • Possible fuel smell or abnormal exhaust

Possible causes

  1. Faulty, clogged or worn cylinder 1 fuel injector
  2. Damaged wiring or poor connection at the injector connector
  3. Fuel delivery problem: low pressure, clogged filter or weak pump
  4. Intake air leak upsetting the air-fuel mixture
  5. Mechanical problem in the cylinder, such as low compression
  6. ECM fault or outdated software (uncommon)

How to diagnose

  1. Scan for all codes and review freeze frame data, looking for related fuel trim or misfire codes
  2. Check fuel trim and injector adaptation values in live data
  3. Run a cylinder balance test and compare rpm contribution per cylinder
  4. Inspect the cylinder 1 injector connector and wiring; test injector resistance and power and ground circuits
  5. Measure fuel pressure and compare it to specification
  6. Look for intake or vacuum leaks (hoses, gaskets, seals)
  7. Check cylinder 1 compression if electrical and fuel checks pass
  8. Swap the injector with a neighboring cylinder to see if the fault follows it

Common fixes

  • Professionally clean or replace the cylinder 1 injector
  • Repair or replace damaged wiring and connectors
  • Fix the fuel supply issue: filter, pump or pressure regulator
  • Repair any intake air leaks
  • Reset injector adaptations and update ECM software if available

Questions and answers

What does P02CD mean?

The ECM has run out of correction range for the cylinder 1 injector and can't compensate for the fuel delivery error any more. The cause is usually the injector, its wiring or fuel supply.

Can I just clear P02CD?

Clearing it only turns the light off for a while. If the root cause remains, the learned value will hit the limit again and the code will return.

Do I always need a new injector?

No. Cleaning the injector or repairing a connector or wiring fault can fix it. Replace the injector after you have checked fuel pressure, air leaks and the electrical circuit.

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.