[aldred309uk]

Originally Posted by canis

I'm sorry if I've given the wrong impression! I'm nowhere near knowledgeable on this subject - I only know what i've read, desperately trying to scrape my cars through their MOTs each year like yourself.

Are you absolutely certain the cat was changed for a new one? It's doubtful it would fail so quickly, unless it was burnt out by some other problem (unburnt fuel?) prematurely. They're supposed to last for years.

I'm sure there are forum users who know more about this than me. I would've thought they'd have something to say on this thread by now, I sure hope they do.

I would hazard that the lambda sensor and cat have similar life expectancy. They work by chemical reaction, and don't last forever, so if it's on it's original sensor it's entirely likely it's at the end of it's life. They don't entirely stop working, they emit (or affect in some way) a pulse of electricity according to gases present, but as they age the range between high and low becomes thinner. I've often wondered if their life could be extended crudely by amplifying this effect, in a smiliar way to how LAN repeaters extend range, but i've never put any experiments into action. After my kitten relieved itself on my ancient oscillloscope, such experiments are rendered beyond my technology. I went through all this with my old Sierra.

As in the previous post, the best bet is to get codes read if you can. Otherwise, it's down to buying sensors and replacing them until the problem is fixed. Which sucks, but it's the only option really available to a home mechanic stabbing in the dark.

Again, sorry I can't help more.

No problem Haha. Yeah the cat was changed by a garage when it failed and by myself with a brand new part last year. Saxo only gives catalyst inefficiency code when I rear it with a bluetooth reader and torque lite app. Tesco 99 took the light off last time so got half a tank in there now and going for a decent drive to Costco this evening. Mot runs out on the 20th. All is well. Thanks!