Question

On my 2004 Chevrolet Express Van, are P0430 and P0304 related? What do the codes mean?

Answer 1

P0430 Catalyst below efficiency Bank 2

P0304 Misfire number 4 cylinder

Yes it can, The purpose of the CK ENG LT is to protect the catalytic convertor, and catalytic convertor  protects the enviroment from harmful emission emmited into the atmoshere. When there is a misfire this is a code "A" type condition where this is a catalyst damaging condition. The catalytic cannot work properly with this condition. So this is related , and left unrepair for too long P0430 will be the result of a P0304.

Answer 2

P0304 Chevrolet Code - Cylinder 4 Misfire Detected
Read more: https://www.autocodes.com/p0304_chevrolet.html

P0430 Chevrolet Code - Catalyst System Low Efficiency Bank 2
Read more: https://www.autocodes.com/p0430_chevrolet.html