P01D9: Cylinder 8 Injection Timing Performance - Over Retarded

What it means

The control module monitors injection timing performance for cylinder 8. It sets this code when injection timing is more retarded than the allowed range.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The engine control module monitors injection timing performance for cylinder 8 and compares the injector's response with its expected timing. This code sets when cylinder 8's injection event is later than the allowed range, pointing to a possible injector or injection-control fault.

Common causes

Most likely first.

1. Injector or injection control fault

How to diagnose it

1. Save freeze-frame data and check cylinder 8 timing or injector data to establish the conditions when the event was detected as over retarded.
2. Inspect the cylinder 8 injector and connector for damage, contamination, loose fit, or fuel leakage.
3. Compare cylinder 8 contribution and injector response with the other cylinders using available scan-tool data.
4. Test the cylinder 8 injector wiring and control circuit for opens, shorts, and poor connections following the manufacturer's procedure.
5. If the circuit checks pass, evaluate the injector's operation and fuel delivery against the manufacturer's specification.

Common fixes

• Reconnect or repair a poor cylinder 8 injector connector or damaged wiring.
• Correct a fuel delivery problem if testing finds one.
• Clean or replace a sticking or faulty cylinder 8 injector.
• Repair the injector control circuit if tests identify a driver or wiring fault.

Can I keep driving?

A steady warning light with normal engine operation usually permits a short, gentle trip for diagnosis, but avoid hard acceleration and towing. Stop if the engine begins to misfire, runs roughly, or loses power, as continued poor combustion can worsen emissions and damage exhaust components.