Leaking or over-delivering fuel injector on cylinder 3; Fouled, worn or incorrectly gapped spark plug or weak ignition coil on cylinder 3 causing incomplete combustion; Damaged wiring, poor connector contact or corrosion in the cylinder 3 injector circuit; Mechanical fault on cylinder 3 such as low compression, a burnt valve or carbon build-up affecting airflow; Fuel pressure too high or a fault in the fuel pressure control, which pushes all cylinders rich and shows up on the weakest one; Faulty oxygen or air-fuel ratio sensor, or an exhaust leak, giving misleading mixture feedback; Outdated or faulty ECU software where a known fault is documented for the specific engine.

P02A3

Cylinder 3 - Fuel Trim at Min 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)
A3: FaultThe specific fault in that area

What it means

P02A3 means the engine control unit has found that the individual fuel correction for cylinder 3 has reached its minimum limit, so it cannot remove any more fuel from that cylinder. The ECU saw cylinder 3 running richer than expected, or its per-cylinder balance reading indicating excess fuel, and it had no further correction available. Cylinder-specific monitoring and the method used differ between engines, so the exact test depends on the model.

Symptoms

Rough idle or misfire feel, particularly when warm
Engine management light on
Higher than normal fuel consumption
Smell of unburnt fuel from the exhaust
Hesitation or uneven running under light load
Possible black smoke or sooty tailpipe

Possible causes

Leaking or over-delivering fuel injector on cylinder 3likely
Fouled, worn or incorrectly gapped spark plug or weak ignition coil on cylinder 3 causing incomplete combustionlikely
Damaged wiring, poor connector contact or corrosion in the cylinder 3 injector circuitpossible
Mechanical fault on cylinder 3 such as low compression, a burnt valve or carbon build-up affecting airflowpossible
Fuel pressure too high or a fault in the fuel pressure control, which pushes all cylinders rich and shows up on the weakest onepossible
Faulty oxygen or air-fuel ratio sensor, or an exhaust leak, giving misleading mixture feedbackrare
Outdated or faulty ECU software where a known fault is documented for the specific enginerare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting engine temperature, load and fuel trim values at the time the code set
Check for other fuel trim, misfire or injector codes, since these help show whether the problem is isolated to cylinder 3 or affects the whole engine
Inspect the cylinder 3 injector connector and wiring for damage, corrosion, heat damage or loose pins
Remove and inspect the cylinder 3 spark plug and check the coil for signs of fuel fouling, cracking or tracking, comparing with the other cylinders
Compare live fuel trim and misfire counter data for each cylinder at idle and under light load to confirm that cylinder 3 is the outlier
Test the injector on cylinder 3 for resistance, leak-down and spray pattern or flow against specification, following the procedure for the engine
Measure fuel pressure and check the regulation against the manufacturer specification
Carry out a compression or leak-down test on cylinder 3 if electrical and fuel checks are clear

How to fix

Replace or professionally clean and recalibrate the cylinder 3 injector if it leaks or over-delivers
Replace the spark plug or ignition coil on cylinder 3 if they are worn or faulty
Repair damaged wiring or connector terminals in the injector circuit
Correct fuel pressure faults by repairing or replacing the faulty regulator, pump control or sensor as diagnosed
Repair the mechanical fault found on cylinder 3, such as valve or compression problems
Update the ECU software only if the manufacturer documents an outdated calibration as a known cause for this engine

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but book it in soon. Excess fuel can wash oil from the cylinder wall, foul plugs and overheat the catalytic converter, so avoid hard driving until it is fixed.

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