P0420 Catalyst System Efficiency Below Threshold

[Tony.F]

Hi, New here, Just bought a 2004 Rav4 2.0 L Petrol VVti, all is good, except for this engine management light warning and an error code "P0420 Catalyst System Efficiency Below Threshold"

I have cleared the code many times and it comes back on within 100 miles

Local Garage has checked the cat - All OK & emmisions all within good levels, Replaced front O2 sensor and Rear O2 sensor, so everything seems to be working - Strange!

Any Ideas what else may cause this?

Anyone seen this before?

Help, Tony.

 

[IanML]

Just wondering what could lead to a faulty diagnosis, and, tentatively, the coolant temperature sensor comes to mind.

However, it could be that the Cat diagnosis is more sensitive than the emission test limits, and the cat really is on the way out.  Do you have the previous MOT test readings to compare?

[Tony.F]

Thanks, I will check coolant sensor.

Unfortunately, Just got the car, don't have the previous emissions results