P021B: Cylinder 8 Injection Timing

What it means

The PCM detected a problem with injection timing for cylinder 8. 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 8, though the timing method varies by engine. The PCM monitors cylinder 8's injection timing or injector response and sets P021B when that cylinder's behavior does not match the expected timing.

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, noting whether cylinder 8 symptoms appear at startup, idle, or under load.
2. Identify cylinder 8 from vehicle service information and inspect its injector connector and wiring for damage or poor contact.
3. Test cylinder 8's injector control circuit for opens, shorts, and high resistance using the manufacturer's procedure.
4. Check cylinder 8 injector operation or timing data and compare it with the other cylinders using the appropriate scan-tool functions.
5. If the circuit checks out, verify fuel pressure and test cylinder 8's injector response against the manufacturer's specification.

Common fixes

• Reconnect or repair cylinder 8 injector wiring.
• Clean or repair corroded terminals at the cylinder 8 connector.
• Replace a cylinder 8 injector that fails testing.
• Correct a verified fuel-pressure or delivery fault.
• Repair a confirmed timing-control problem affecting cylinder 8.

Can I keep driving?

Limit driving if the engine misfires or loses power, and avoid hard acceleration because an ongoing misfire can damage the catalytic converter. Stop if the warning flashes or the engine becomes severely rough.