P02A7
Cylinder 4 - 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)
- A7
- FaultThe specific fault in that area
What it means
P02A7 means the engine control unit has found that the individual fuel correction for cylinder 4 has reached its minimum limit. The ECU is taking away as much fuel as it is allowed to on that cylinder, yet still sees a rich condition there. This code only applies to engines that track cylinder-by-cylinder fuel trim, so the exact method of detection varies by model and engine.
Symptoms
- Engine management light on
- Rough idle or uneven running, especially when warm
- Noticeably worse fuel economy
- Smell of unburnt fuel from the exhaust
- Hesitation or misfire on light throttle
- Possible black smoke or sooty tailpipe
Possible causes
- Leaking or sticking fuel injector on cylinder 4 delivering too much fuellikely
- Injector wiring, connector or driver fault affecting cylinder 4 injectorpossible
- Fuel pressure too high, for example a faulty regulator or pressure control fault, which may show on other cylinders toopossible
- Fouled or faulty spark plug or ignition coil on cylinder 4 causing incomplete combustion that the sensors read as richpossible
- Exhaust gas sensor fault or contaminated sensor giving a false rich reading for that cylinder's bankpossible
- Mechanical problem on cylinder 4 such as low compression or a restricted intake runner affecting the air-fuel balancerare
- Outdated or faulty ECU software where a known fault is documented by the manufacturerrare
How to diagnose
- Read all stored and pending codes and the freeze frame data; note whether other fuel trim, misfire or injector codes are present
- Check live fuel trim values, both short and long term, and cylinder 4 individual trim compared with the other cylinders
- Inspect the cylinder 4 injector connector and wiring for damage, corrosion, chafing or loose pins
- Inspect spark plugs and coils, comparing cylinder 4 with the others for fouling, wear or fuel contamination
- Measure fuel pressure against the manufacturer specification and check for pressure bleed-down after shutdown
- Test the cylinder 4 injector electrical resistance and operation, and look for leakage or a poor spray pattern as the procedure for your model allows
- Check oxygen or air-fuel sensor readings and look for exhaust leaks or contamination near the sensors
- Perform a compression or leak-down test on cylinder 4 if the fuel and ignition checks find nothing
How to fix
- Replace or professionally clean and flow-test the faulty cylinder 4 injector
- Repair or replace damaged injector wiring or connectors
- Correct the fuel pressure fault by repairing or replacing the faulty regulator, pump control or related component
- Replace worn spark plugs or a failing ignition coil on cylinder 4
- Replace a faulty exhaust gas sensor once testing confirms it is at fault
- Update the ECU software only if the manufacturer lists it as a fix for this fault, then clear codes and confirm with a road test
Can I keep driving?
Medium severity
The car can usually be driven for a short time, but book it in soon. Running rich can wash oil from the cylinder wall, dilute engine oil and overheat the catalytic converter, so avoid long journeys or hard driving.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.