2001 Nissan Pathfinder OBDII P0420. Which parts should be replaced in order for the cehicle to pass the SMOG Test?

Question

When doing a diagnostic test, it indicated codes P0420, P1491, P0158 and P0159.

Answer 1

if you have all those codes, you should fix them one by one, the  O2 sensors might need to replaced first

P0159 NISSAN - HO2S22 Slow Response

Possible causes

- Rear Heated Oxygen Sensor Bank 2 harness is open or shorted
- Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection
- Faulty Rear Heated Oxygen Sensor Bank 2
- Inappropriate fuel pressure
- Faulty fuel injectors
- Intake air leaks may be faulty
- Exhaust gas leaks

Replacing the O2 Sensor 2 usually takes care of the problem

 

 

P0420 NISSAN - Catalyst System Efficiency Below Threshold Bank 1

Possible causes

- Three way catalyst converter Bank 2
- Engine Control Module (ECM) Program
- Exhaust tube
- Intake air leaks
- Fuel injectors may be faulty
- Fuel injector leaks
- Spark plugs may be faulty
- Improper ignition timing
- Engine Control Module

Possible solution

The most common cause it the three way catalyst converter Bank 1. Changing just the O2 sensor usually don't repair the problem.

 

https://www.autocodes.com/p0420_nissan.html

 

P1491

Possible causes

- Vacuum cut valve bypass valve
- Vacuum cut valve
- Bypass hoses for clogging
- EVAP control system pressure sensor and circuit
- EVAP canister vent control valve
- Hose between fuel tank and vacuum cut valve clogged
- Hose between vacuum cut valve and EVAP canister clogged
- EVAP purge port of fuel tank for clogging

 

https://www.autocodes.com/p1491_nissan.html