P021C: Cylinder 9 Injection Timing

What does P021C mean?

P021C reports a fault in the injection timing of cylinder 9 on a diesel engine. Unlike P01DB/P01DC ('over retarded/advanced', the result of the injector learning routine in overrun), this code has no direction, and what it checks is up to the manufacturer. A cylinder 9 code only applies to engines with 9 or more cylinders. No manufacturer or vehicle using it was found – GM's documents stop at cylinder 8 (P021B), FCA's at cylinder 6, and Ford uses other codes. The description therefore follows the documented siblings: GM checks the injector's current rise electrically, FCA ties the code to injector learning. CARB requires diesel engines to detect injection that is too early or too late.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Rough running or misfire, rough idle
• Loss of power, smoke or knocking possible

Common causes

• High Injector of cylinder 9 faulty (coil, armature, wear, deposits)
• Medium Injector wiring or connector: contact resistance, corrosion, chafing
• Low Engine software sets the code falsely (update available for some models)
• Low Injector driver stage or boost voltage in the engine module
• Low Wrong injector code, contaminated fuel or loose injector clamp

Likelihood is a general estimate across vehicles; your make and model may differ.