Intermediate
5 min read
· OBD Code Mastery
Top 10 Fleet DTC Codes and What To Do
P0300, P0171, P0420, P20EE, U0100 — the codes fleet managers see most. Severity ratings, common causes, and repair cost estimates.
Key Facts
- P0300 (misfire): can damage catalytic converter — schedule in 48 hours
- P20EE (SCR/DEF): vehicle may derate to 5 mph — service immediately
- U0100 (lost ECM comms): STOP — vehicle may stall, tow to shop
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