Mercedes-Benz C 300 2022–2024 — technical service bulletin
Bulletin LI49.20-P-078714 · NHTSA communication 11012060 · issued Dec 20, 2024
Technical service bulletin
communication type
Engine
component
2022–2024
model years
3
vehicle entries
Official summary
Complaint Check engine light illuminated. Fault code P042000 Current or stored in MRG2 control unit. Cause Catalytic converter not operating efficiently Remedy Replace catalytic converter. Note: Additional hardware replacement is not needed unless other symptoms are present. If there are other faults relating to engine operation, diagnose these separately.
What a TSB means. Technical service bulletins are repair guidance manufacturers send to dealers — they are not recalls, and repairs are not automatically free (warranty extensions are an exception worth checking). The full document is available via NHTSA’s vehicle lookup.