Hi,
Relative has a 5 y/o Focus, ECU reports P0420 - Catalyst system efficiency below threshold. I read the code over 6 months ago and said it's likely the cat but could also be the O2 sensors or something else. I advised he take it to a garage and tell them the code, however what he did was take it to a garage and get a new cat fitted which hasn't sorted it! Groan (and yes they did drive it for over 6 months with the check engine light on).
Anyway, to avoid costly further mistakes can someone tell me how to determine if the O2 sensors are working right and if there's any other likely problems to check for? I have got something that lets me see in real-time the various values the ECU reports and among them are the O2 sensor outputs, should make things easier if the Focus ECU actually sends the values. I don't know what to look for though!
Something that might be related is that I have to keep pointing out to them (and they take no notice) is that they never exceed 2000rpm unless in top gear, often I see them try to accelerate from well under
1k and feel the engine vibrate through the chassis, often as a result of thinking that you can't possibly use 1st for more than 5 seconds under any circumstances.My limited understanding of this is that it means that it'll be running rich most of the time, could that have a bearing on this?
Thanks again,
Peter.