What it means
The control module detected restricted fuel flow through the cylinder 4 injector. The code identifies a flow restriction, but does not specify its cause.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Cylinder 4’s injector meters fuel into that cylinder in response to commands from the engine control module. The module evaluates whether fuel delivered through this injector appears restricted and sets P02A8 when flow is below the expected level.
Common causes
Most likely first.
- Injector nozzle clogged or contaminated
- Restricted fuel supply to injector
- Injector electrical or control fault
- Fuel contamination
Symptoms
- Check-engine light
- Rough idle or engine vibration
- Misfire or hesitation
- Reduced engine power
How to diagnose it
- Record freeze-frame data and check live misfire and fuel-trim readings to see when cylinder 4’s fueling problem occurs.
- Inspect cylinder 4’s injector connector and wiring for looseness, damage, corrosion, or signs of fuel contamination.
- Check fuel quality and inspect the supply to cylinder 4’s injector for a restriction.
- Use an appropriate scan-tool or electrical test to check whether the module is commanding cylinder 4’s injector and whether its circuit responds.
- Compare cylinder 4 injector flow with the other cylinders using the vehicle maker’s approved test procedure.
Common fixes
- Repair a loose or damaged cylinder 4 injector connector or wiring.
- Correct a restriction in the fuel supply to cylinder 4’s injector.
- Clean or replace the restricted cylinder 4 injector as appropriate.
- Repair the injector control circuit if testing identifies an electrical fault.
- Replace contaminated fuel and address its source.
Can I keep driving?
Avoid hard acceleration and long trips while cylinder 4 is running rough or misfiring; continued driving can worsen performance and increase emissions. If the engine shakes severely or the check-engine light flashes, stop driving and arrange prompt diagnosis.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.