Faulty fuel injector for cylinder 8 (internal solenoid or nozzle issues); Damaged or corroded wiring harness or connector at the cylinder 8 injector; Failed camshaft position sensor or crankshaft position sensor providing inaccurate timing signals; Sticking or contaminated injector causing incorrect injection timing; ECM software calibration issue or internal fault in the injector driver circuit; Low fuel pressure or restricted fuel flow affecting injection timing; Mechanical issues such as a worn camshaft lobe or lifter affecting valve timing

DTC codes / P02xx · Fuel and air metering (injector circuits) / P021B

P021BCylinder 8 Injection Timing

Q: What does code P021B mean?

Cylinder 8 Injection Timing. P021B is a generic powertrain code indicating that the engine control module (ECM) has detected an out-of-range condition in the injection timing circuit for cylinder number 8. The ECM monitors the commanded injection timing versus the actual feedback signal from the injector or the camshaft position sensor, and it sets this code when the timing deviates beyond a calibrated threshold. This code is specific to the eighth cylinder and does not directly affect other cylinders unless the root cause is shared.

P021B is a generic powertrain code indicating that the engine control module (ECM) has detected an out-of-range condition in the injection timing circuit for cylinder number 8. The ECM monitors the commanded injection timing versus the actual feedback signal from the injector or the camshaft position sensor, and it sets this code when the timing deviates beyond a calibrated threshold. This code is specific to the eighth cylinder and does not directly affect other cylinders unless the root cause is shared.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or misfire sensation, especially noticeable at low speeds
Reduced engine power or sluggish acceleration
Increased fuel consumption due to inefficient combustion
Occasional engine hesitation or stumble during acceleration
Possible black smoke from the exhaust if the injector is over-fuelling

Common causes, most likely first

Faulty fuel injector for cylinder 8 (internal solenoid or nozzle issues)
Damaged or corroded wiring harness or connector at the cylinder 8 injector
Failed camshaft position sensor or crankshaft position sensor providing inaccurate timing signals
Sticking or contaminated injector causing incorrect injection timing
ECM software calibration issue or internal fault in the injector driver circuit
Low fuel pressure or restricted fuel flow affecting injection timing
Mechanical issues such as a worn camshaft lobe or lifter affecting valve timing

How to diagnose and fix it

Use an OBD-II scanner to verify the code and check for related codes (e.g., misfire, camshaft/crankshaft sensor codes).
Inspect the wiring and connector at the cylinder 8 fuel injector for damage, corrosion, or loose pins; repair or replace as needed.
Test the fuel injector resistance and compare to specification; replace if out of range.
Check fuel pressure and volume to ensure the system meets manufacturer specifications.
Perform a injector balance test or use a lab scope to observe the injector pulse width and timing signal.
Inspect the camshaft and crankshaft position sensors for proper signal and mounting; replace if faulty.
If all else fails, reprogram or replace the ECM after confirming no other faults exist.

Cylinder 8 timing faults often misdiagnosed

A dirty or failing injector for cylinder 8 can cause timing deviations without setting a misfire code, so injector cleaning or replacement is often the fix.
Wiring harness chafing near the cylinder 8 injector is common on engines with tight routing, and a visual inspection may reveal rubbed insulation.
The code can be set by a weak camshaft position sensor that only misbehaves when hot, so testing the sensor when cold may miss the fault.
Low fuel pressure from a tired fuel pump can affect injection timing on one cylinder more than others, especially under load.
Replacing the ECM without first verifying the injector driver circuit and wiring is a costly mistake that rarely solves the problem.

Can I keep driving with P021B?

You can drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing because continued driving with incorrect injection timing can damage the catalytic converter or cause engine misfire. If the check engine light flashes, stop driving immediately and seek professional diagnosis.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.