Failed the DEQ test with a trouble code P0421. Had a local mechanic do a cat test, he said the cat was clogged but using premium fuel whould clear it up and to try DEQ again. Failed DEQ again with the same code and then got a cat test by a franchise mechanic, they said I had to replace the cat and o…

UncleTurbo June 14, 2012, 3:05am 3

Seems like I’d let the local mechanic run some tests. The frachise place is just replacing lots of parts figuring one of them will take care of the failed DEQ test.

DEQ fail P0421 - Warm up Catalyst Efficiency Below Threshold (Bank 1)