Fault code P0420, further diagnosis

[fathands]

Hello,

I’ve had the following code pop up on my diagnostics for a while now. 
looking at it’s description it is either:

Possible Causes

• Leakage in Intake and/or Exhaust System
• Catalyst faulty
• Oxygen Sensor(s) faulty
• Oxygen Sensor(s) Control fault

i don’t really want to just start throwing money at it by replacing a part at a time, is there any way to diagnose further?

Which o2 sensor may be faulty, how do I test them and what readings are out of tolerance?

I assume if the o2 sensors are testing ok, then the catalyst is likely to be the issue?

Any help would be greatly appreciated. 
 

Thanks

Andrew

Photo.pdf

[Stevey Y]

7 hours ago, fathands said:

Hello,

I’ve had the following code pop up on my diagnostics for a while now. 
looking at it’s description it is either:

Possible Causes

• Leakage in Intake and/or Exhaust System
• Catalyst faulty
• Oxygen Sensor(s) faulty
• Oxygen Sensor(s) Control fault

i don’t really want to just start throwing money at it by replacing a part at a time, is there any way to diagnose further?

Which o2 sensor may be faulty, how do I test them and what readings are out of tolerance?

I assume if the o2 sensors are testing ok, then the catalyst is likely to be the issue?

Any help would be greatly appreciated. 
 

Thanks

Andrew

Photo.pdf 25.73 MB · 3 downloads

Hi its probably the Cat becoming clogged my first go personally would be to give it a dose of Cataclean then  if its still playing up you may well have to replace both oxygen sensors as generally speaking they trade information and if you renew one on a car that old it will cause the other older sensor to fail, trying to test oxygen sensors that old would be a waste of time, try the cleaner first.

Steve.

[fathands]

Thanks. 
I’ll give that a go and report back. 

[fathands]

Doesn’t seem to have made any difference unfortunately. 
Does that leave me with no option other than to start replacing parts?

 Thanks 

Andrew