02 December, 2025PACCAR MX (2004 Emissions) Fault Code: P2238 Lambda – Current Too Low on ECU (D420) Pin (C45) PACCAR MX (2004 Emissions) Fault Code: P2238 Lambda – Current Too Low on ECU (D420) Pin (C45) SET CONDITIONS:The PCI ECU (D420) detects a lower current than expected in the measuring circuit of the lambda sensor. DIAGNOSTIC CONDITION:The diagnostic runs continuously when the ignition is keyed on. RESET CONDITION:The DTC changes to inactive after the diagnostic runs and passes. POSSIBLE CAUSES:1. Lambda sensor wiring issue2. Lambda sensor failure Share on Facebook Opens in a new window. Tweet on Twitter Opens in a new window. Pin on Pinterest Opens in a new window. Back to blog