Question

2004 Hyundai Santa Fe with engine codes P0304 and P0421, what is the meaning of the codes?

Answer 1

Hi there,

These codes are for a #4 cylinder misfire (P0304) and the bank 1 pre catalytic converter which is the small one directly off the exhaust manifold. I would start by replacing the #4 ignition coil, then clear the codes and see if the converter code returns.

Answer 2

P0304 HYUNDAI Code - Cylinder 4 Misfire Detected
Read more: https://www.autocodes.com/p0304_hyundai.html

P0421 HYUNDAI Code - Warm Up Catalyst Efficiency Below Threshold Bank 1
Read more: https://www.autocodes.com/p0421_hyundai.html