P021C: Cylinder 9 Injection Timing

What it means

The PCM detected a problem with injection timing for cylinder 9. The precise monitoring method and cause depend on the engine and injection system.

At a glance

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

How it works

The injection system controls when fuel reaches cylinder 9, with the exact method depending on the engine design. The PCM monitors cylinder 9's injection timing or injector response and sets P021C when that cylinder's timing behavior is outside the expected range.

Common causes

Most likely first.

1. Injector timing or response fault
2. Injector wiring or connector fault
3. Fuel injector fault

Symptoms

• Check-engine light on
• Rough running or misfire
• Reduced engine power
• Hard starting

How to diagnose it

1. Record freeze-frame data and related codes, and check whether cylinder 9 symptoms are worse at startup, idle, or under load.
2. Confirm cylinder 9's location from vehicle service information, then inspect its injector connector and wiring for damage or loose contacts.
3. Test cylinder 9's injector circuit for opens, shorts, and poor connections using the manufacturer's procedure.
4. Compare cylinder 9 injector timing or response data with other cylinders using the appropriate scan-tool function.
5. If the circuit passes, check fuel pressure and cylinder 9 injector response against the manufacturer's specification.

Common fixes

• Secure or repair damaged wiring to the cylinder 9 injector.
• Clean or repair poor electrical contact at the cylinder 9 connector.
• Replace a cylinder 9 injector that fails its operational test.
• Correct a confirmed fuel-pressure or delivery problem.
• Repair a verified timing-control fault affecting cylinder 9.

Can I keep driving?

Avoid heavy loads if the engine runs roughly or has reduced power, since a continuing cylinder 9 misfire can overheat the catalytic converter. Stop driving if the warning flashes or the engine shakes severely.