Mercedes-Benz C 300 2022–2025 — technical service bulletin
Bulletin LI20.10-P-078510 · NHTSA communication 11014223 · issued Feb 6, 2025
Technical service bulletin
communication type
Engine
component
2022–2025
model years
9
vehicle entries
Official summary
Complaint Red cooling system malfunction warning due to overheat. Low engine performance. Check engine light on. Fault codes may be stored: P21814B The cooling system has a malfunction. There is a fault due to overtemperature. P2B8500 The rpm of the coolant pump is too low. Cause Various Remedy Check for loose plug at electrical connectors of high temp coolant pump (M43/10 or M75/11) by gently pulling on connector housings. Create a TIPS case and submit to powertrain team inbox if a loose plug is found at the coolant pump. Include: -Initial quick test -Details on any damage found to engine or
Vehicles covered
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.