OBD fault code library
Look up any P or U code to see what it means, what causes it, the parts involved and how it gets fixed.
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OBD DashX shows which problems come with each code, how often they show up in other vehicles, and how to fix them — step by step.
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Fault codes
P2004
Particulate trap efficiency lower than limits
Mercedes Benz
Auxiliary Emissions Control
High severity
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Read and clear fault codes, live data and service resets with the CaRPM app.