03 December, 2025PACCAR MX (2004 Emissions) Fault Code: P109C Common Rail Pressure Release Valve – Current Too Low or Open Circuit on ECU (D420) Pin (C4) PACCAR MX (2004 Emissions) Fault Code: P109C Common Rail Pressure Release Valve – Current Too Low or Open Circuit on ECU (D420) Pin (C4) POSSIBLE CAUSES:No repairs are necessary. ADDITIONAL INFORMATION:Do not troubleshoot this DTC. Compartir en Facebook Se abre en una nueva ventana. Compartir en Twitter Se abre en una nueva ventana. Guardar en Pinterest Se abre en una nueva ventana. Regresar al blog