Usamos cookies para análisis básicos — nada se carga hasta que aceptes. Puedes rechazar y seguir navegando con normalidad. Política de Privacidad
Diagnostic trouble code P21C9 indicates: Reductant Control Module Power Relay/Relays Control Circuit High. It was set by your vehicle's onboard diagnostics system and will typically keep the check engine light on until it's addressed.
Upload your ECU file and DTC Doctor will detect this code (and any others) automatically, then remove it for good — no dealer visit, no guesswork.
Analyze My File Free →