P21BB: Cold Start Cylinder 6 Injection Timing

What it means

Cylinder 6 cold-start injection timing is outside the calibrated range. The code does not by itself identify the cause.

At a glance

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

How it works

During a cold start, the engine control module calculates injection timing for cylinder 6 from crankshaft and camshaft position and other engine data. This code sets when cylinder 6's cold-start injection timing is outside the calibrated range, which can involve injector wear or control, fuel delivery, or timing signals.

Common causes

Most likely first.

1. Cylinder 6 injector wear or altered flow
2. Injector wiring or control fault
3. Fuel pressure or delivery problem
4. Crank or cam timing signal issue

Symptoms

• Check-engine light
• Rough running or misfire after a cold start
• Hard starting when the engine is cold
• Increased exhaust smoke

How to diagnose it

1. Save freeze-frame data and examine cylinder 6 cold-start timing and misfire data during a cold start, noting coolant temperature and fuel pressure.
2. Inspect the cylinder 6 injector connector and wiring for damage, corrosion, loose pins, or poor contact.
3. Check for related injector, fuel-pressure, crankshaft, camshaft, and correlation codes that may reveal a common cause.
4. Compare cylinder 6 injector correction or balance data with the other cylinders during the same cold-start conditions.
5. Test cylinder 6 injector flow and control, then verify crank and cam signals and mechanical timing if initial checks do not explain the deviation.

Common fixes

• Repair damaged or loose cylinder 6 injector wiring or connections.
• Correct a confirmed fuel-pressure or delivery fault.
• Service or replace the cylinder 6 injector if its flow or control is out of specification.
• Repair a faulty crankshaft or camshaft signal, or correct verified mechanical timing error.

Can I keep driving?

Limit driving and arrange diagnosis soon if the engine runs normally once warm, since cold-start misfire and smoke can raise emissions and may worsen. Do not continue driving with a severe misfire, flashing warning, or unreliable starting.