p0420 Catalyst Efficiency Below Threshold - Fixed

[RX-Men-8]

Hi,

Just to share a successful €15 mod with the forum :)

My 2004 Avensis Versio 2.0 VVT-i threw a CEL (Check Engine Light) regularly when driving slow for a longer period of time, with trouble code:

P0420 Catalyst System Efficiency Below Threshold Bank 1

The car always passed the emission tests so I reset the error code every time it happened.  But it gradually started to happened more often so I wanted to do something about it other than always putting my foot down to keep the ecu in open loop ;)  On top of that I noticed this winter that while the TRC OFF and VSC lights light up together with these codes, the TRC and VSC are actually off and not functioning when this happens, and that is a bad thing.  Even bad design if you ask me to have these safety features disable just to draw attention to the catalyst converter.

I did some internet research and read that the ECU compares the readings of O2 sensor 1 (before the main cat) and O2 sensor 2 (between the main cat and 2nd cat).  If the readings are too similar it decides the cat efficiency is too low.  There are spacers on eBay to keep O2 sensor 2 a bit more out of the exhaust flow so it reacts slower to the exhaust fluctuations.  This is what these look like:

The small hole only lets a bit exhaust gas in, so the idea is that the O2 sensor is out of the main flow and will react slower to changes in the exhaust flow.

Fitted it looks like this (I had to cut off the stainless steel protective baffle around the sensor to get it out as it was really hard to get the sensor loose):

  

And, so far so good, 2 weeks without trouble codes :)

BTW, for my Avensis Verso it is known that the ECU is a bit too sensitive about O2 readings

Greetings, Gerhard

[Cose]

It's works that? Thx