Question

2007 Mitsubishi Galant 2.4L with engine codes P0420 and P0423, what needs to be replaced?

Answer 1

HI there,

both these codes are for the catalytic converter working below threshold. The most common repair for this is to replace the pre cat right off th exhaust manifold. This is the converter between the front and rear O2 sensors.

Answer 2

P0420 MITSUBISHI Code - Catalyst System Efficiency Below Threshold Bank 1
Read more: https://www.autocodes.com/p0420_mitsubishi.html