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High Nox Reading — Possible Fault Codes

Found 4 fault codes associated with high nox reading. Codes are sorted by severity — check STOP ENGINE codes first.

SPN 4342 FMI 4

NOx Sensor Outlet

Detroit Diesel DD13 • Component: NOx Sensor (Outlet) / Wiring • J1939

🟠 CHECK SOON

SPN 4364 FMI 18

SCR NOx Conversion Low

International A26 • Component: SCR Catalyst System / DEF Dosing • J1939

🟠 CHECK SOON

SPN 4364 FMI 18

SCR NOx Conversion Low

Detroit Diesel DD13 • Component: SCR Catalyst System / DEF Dosing • J1939

🟠 CHECK SOON

SPN 3556 FMI 5

NOx Sensor Heater Circuit Fault

PACCAR MX-13 • Component: NOx Sensor (Outlet) / Heater Circuit / Wiring • J1939

🟠 CHECK SOON

⚠️ Diagnostic Note: Symptoms can have multiple root causes. Always verify with a diagnostic scan tool before replacing parts. The fault codes listed above are possible matches for high nox reading based on SAE J1939/J1587 fault code definitions and OEM service documentation.