Cylinder 1 injector worn, sticking, leaking or partly blocked, so delivery differs from the commanded amount; Wiring or connector fault at the cylinder 1 injector, such as high resistance, corrosion or a poor pin fit; Low or unstable fuel pressure or poor fuel quality affecting injector delivery; Carbon build-up or a mechanical fault on cylinder 1, such as low compression or intake deposits, changing the combustion the ECU is correcting for; Recently fitted injector not coded or learned to the ECU, or the learned values were not reset after the repair; Outdated or faulty ECU calibration where a known issue exists for the engine; Internal ECU injector driver fault.

P02CD

Cylinder 1 Fuel Injector A Offset Learning At Max Limit.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
2: AreaFuel and air metering (injector circuit)
CD: FaultThe specific fault in that area

What it means

P02CD means the engine control unit has learned a correction for the cylinder 1 fuel injector (injector A) and that correction has reached its maximum limit. The ECU adjusts injector offset to match the fuel actually delivered to the amount it commanded, and it can no longer compensate for the difference. The exact learning method and the limits vary by engine and manufacturer.

Symptoms

Engine management light on
Rough idle or uneven running, mainly on cylinder 1
Misfire or hesitation under load
Poor fuel economy
Hard starting or extended cranking
Possible smoke or fuel smell from the exhaust

Possible causes

Cylinder 1 injector worn, sticking, leaking or partly blocked, so delivery differs from the commanded amountlikely
Wiring or connector fault at the cylinder 1 injector, such as high resistance, corrosion or a poor pin fitlikely
Low or unstable fuel pressure or poor fuel quality affecting injector deliverypossible
Carbon build-up or a mechanical fault on cylinder 1, such as low compression or intake deposits, changing the combustion the ECU is correcting forpossible
Recently fitted injector not coded or learned to the ECU, or the learned values were not reset after the repairpossible
Outdated or faulty ECU calibration where a known issue exists for the enginerare
Internal ECU injector driver faultrare

How to diagnose

Read all stored and pending codes and the freeze frame data, and note any related misfire, fuel trim or fuel pressure codes
Check for relevant technical service bulletins and software updates for the vehicle and engine
Inspect the cylinder 1 injector connector and wiring for damage, corrosion, heat damage and a secure fit
Check fuel quality and the fuel level, and look for signs of contamination
Review live data for injector correction values on all cylinders and compare cylinder 1 with the others
Measure fuel pressure and check it against the manufacturer's specification at idle and under load
Carry out an injector balance or leak-off test, where the engine type allows it, and check injector resistance against specification
Check cylinder 1 compression and inspect the intake for deposits if the injector tests are good

How to fix

Repair or replace damaged wiring or connectors for the cylinder 1 injector
Clean or replace the faulty cylinder 1 injector, and code or learn the new injector to the ECU as the manufacturer requires
Correct fuel supply problems, such as pressure faults or contaminated fuel
Repair the underlying mechanical fault on cylinder 1, such as compression loss or heavy intake deposits
Apply an ECU calibration update only if a bulletin confirms it as a fix for this fault

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but book it in soon, as a poorly performing injector can cause misfires, higher fuel use and possible catalyst or engine damage. Stop driving if the engine runs very roughly, misfires heavily or the warning light flashes.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.