166 gone but not
AO Silver Member
Join Date: Jan 2009
Location: United Kingdom
Re: More engine warning light woes!
Service history says belts were done in 07 @ 46000(ish) by Veloces, so I should be covered on that front (checked that before I brought it). Engine management does measure sensors ie MAF, Lambda, oxygen, etc etc. As my mechanic said (& as I know from experience with computers), ECUs tend to auto-adjust themselves to characteristics as time goes by. If one thing isn't right, it compensates, but this normally "hides" the main fault by adjusting something else.
(Boring techy bit here) Saw this on the Bosch diagnostics myself. Sensors when new turn the cat on & off like a switch. As time goes by the on/off switch becomes slack. When you look at it on a time graph it goes up/down sharply at a constant time rate when new. Over the years the engine management compensates the on/off mechanism & the graph shows the on/off wave does not operate as it should. We are talking tenths & hundreths of seconds here so it's something that only really shows up on diagnostics. Diagnostics also show the voltage of sensors, which should be at a constant level (again, really tiny voltage amounts).
Anybody that has an ODBII scanner, this is not something that shows up on it. This is Bosch diagnostics hardware, which when displayed on a laptop shows just about everything.
I hope I've not bored anybody with this but it's what knowledge I've picked up since looking at engine diagnostics in great detail (my garage understands my passion & they explain it to me as they are running diagostics). My brain takes in as much as it can, but if I'm wrong on any front someone correct me please.