Fuel and air

P021B — Cylinder 8 Injection Timing Fault

Severity: medium Drive with care, to a shop

What P021B means

P021B means the engine control module detected that fuel injection timing for cylinder 8 deviates from the commanded value. The module calculates timing from the crankshaft and camshaft position sensor signals, then fires the injector at the right moment. If the actual injection does not match the plan, or the injector circuit behaves erratically, the code is stored and the check engine light comes on. It is most common on direct-injection engines, including diesels.

Symptoms

  • Check engine light on
  • Misfire or engine stumble
  • Loss of power and sluggish acceleration
  • Rough idle
  • Higher fuel consumption
  • Raw fuel smell or smoky exhaust

Possible causes

  1. Faulty cylinder 8 fuel injector or its solenoid
  2. Open, shorted, damaged or corroded wiring or connector in the injector control circuit
  3. Failing crankshaft or camshaft position sensor, or an erratic signal
  4. Fuel supply problem such as low pressure, clogged filter or weak pump
  5. Air leak skewing the air-fuel mixture
  6. Stretched or slipped timing chain or belt, causing incorrect cam timing
  7. Internal PCM/ECM fault or calibration error (rare)

How to diagnose

  1. Scan all codes and freeze frame data, looking for other injector, misfire or position sensor codes
  2. Review fuel trims or injection adaptation values and run a cylinder balance test
  3. Inspect the cylinder 8 injector wiring and connector for damage, oil and corrosion
  4. Measure injector resistance and test the control circuit for opens and shorts
  5. Check crankshaft and camshaft sensor signals with a scope
  6. Test fuel pressure and inspect the fuel filter
  7. Look for intake and exhaust leaks
  8. Verify timing chain or belt condition and cam timing

Common fixes

  • Replace or repair the cylinder 8 injector
  • Repair damaged wiring and connectors in the injector circuit
  • Replace a faulty crankshaft or camshaft position sensor
  • Fix the fuel supply fault: replace the filter, pump or pressure regulator
  • Correct or replace worn timing components
  • Reflash or replace the PCM only after ruling out everything else

Questions and answers

Can I drive with a P021B code?

Only briefly and only to a repair shop. Incorrect injection timing can cause misfires, power loss, and damage to the catalytic converter or particulate filter.

What most often causes P021B?

Most often it is a bad cylinder 8 injector or a wiring or connector problem at that injector. Position sensors and fuel pressure issues come next.

Will clearing the code fix it?

No. If the cause remains, the code will return. Check the injector, wiring, sensors and fuel system first.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.