Question

2000 Nissan Altima with code P0420, P0325, P0446, P0505, and P1490 where to start?

Answer 1

None of the codes are related. I would start by clearing the code and check what code comes back first. Fix the code and go from there.

P0420 NISSAN - Catalyst System Efficiency Below Threshold Bank 1
Read more: https://www.autocodes.com/p0420_nissan.html

P0325 NISSAN - Knock Sensor Circuit Malfunction
Read more: https://www.autocodes.com/p0325_nissan.html

P0446 NISSAN - Evaporative System Canister Vent Control Valve Circuit
Read more: https://www.autocodes.com/p0446_nissan.html

P0505 NISSAN - Idle Air Control Valve
Read more: https://www.autocodes.com/P0505_nissan.html

P1490 NISSAN - Vacuum Cut Valve Bypass Valve
Read more: https://www.autocodes.com/P1490_nissan.html