Question

My 2002 Mitsubishi Diamante 3.5L V6 came up with the P0421 and P0305 codes, what does it mean?

Answer 1

If there are no intake and exhaust leaks, then the problem is probably the catalytic converter.

P0421 MITSUBISHI - Warm Up Catalyst Efficiency Below Threshold- Cylinders 1-4
Read more: https://www.autocodes.com/p0421_mitsubishi.html

P0305 MITSUBISHI - Cylinder 5 Misfire Condition
Read more: https://www.autocodes.com/p0305_mitsubishi.html