My 2006 Cadillac DTS produces a P0420 and P2431 codes ,a common fix?

Question

The car has 86000 miles and has not had a tune up to my knowledge. What should I do first?

Answer 1

P0420 Catalytic below threshold

P2431 Secondary air injection system pressure signal performance fault

With worn sparkplugs the catalytic convertor has to work much harder in controlling harmful emissions,  The catlytic convertor can only work so much before it wear out, Do a full tune up which includes a air filter and beside it good for your fuel economy. As for P2431 this is more of a secondary air pump that is not turning on for cold start.This has nothing to do wth worn sparkplugs, worn or not the secondary air pump should trun on when suppose to,This can be from the airpump being non op to just the secondary airpump relay.The most probable cause is the secondary air injection check valve,where early start up exhaust condensation corrodes the air check valve.