p0421

  1. originalmarshmello

    [SOLVED] How do I avoid a CEL with a catless DP?

    Just installed my turboxs catless downpipe and racepipe on my 09 gen 1 speed3. It sounds awesome. However, roughly 30 miles after the install, 3 miles into the third drive after the install (which I didn’t let it sit and warm up because I had to get somewhere), it threw a CEL with a P0421 code...
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