MCSF - interesting discovery
So I think my case is specific but for much of the last 9 months my yellow light has been on/off for days, sometimes months at a time with never bad affects, ie if the light on the dash did'nt exist then I would never have known anything was wrong. When off, it always came on ~5 miles into the journey and codes stored showed out of range err.
Dealer had it once, had to capture the fault in real time, which they did and changed lambda, but then of course the light came on shortly afterwards so clearly they had no idea either.
Anyway, topping up with oil the other day, I had a play around with my torch to look at all four sensors ( light been on for about 6 weeks ). I noticed the bottom sensor cable leading up to the loom connector was hanging free and indeed resting on the manifold. I thought then that the cable would be stuck as it would be melted on, but no it was free and I clipped in back up into the half broken loom clip. 3 starts later the light goes off, so I think as the exhaust got hot it shorted out one of the sensor wires and threw in the duff reading.
However this theory suggests once shorted then permanetly a problem, but I know the light only came on as the car went from cold to hot ( if off ), so the heat of the manifold maybe interfered with the current in the wire and it was not a short. I know the sensors are very sensitive and work from an oscillating signal, so maybe the exhaust gets hot and gives off enough signal noise to affect the signal in the cable.
Anyway, thought I'd share this as simple clip in of a cable turned the light off instantly.
The problem only happened soon after the 36K cam belt change so I think a fair amount of tugging just prised the cable out
I hope my mystery is solved.
There's nothing in the dark that isn't there in the light ..... except fear