Funny thing happened to me and my Aug 04 build 05 MCS yesterday. Motored up to the top of Mt Evans (14,264 ft) west of Denver (5,280 feet) car did great going up; no oxygen issues with the supercharger.

Anyway, after some time at the top, we get back in and the SES lite stays on: the first time in over 7000 miles. Also, the ASC (off) lite stays on, and it won't go away when I hit the toggle. I figured get back to a lower altitude and both will go away. Not so.

Get back to Denver, go have dinner, come out, and while the SES lite is still blaring its yellow lite, at least the ASC is back to normal. Methinks the ASC issue is one with high altitudes and tire pressure causing a misread?

As far as the car goes, there's no drop in performance or mileage, so I don't see it as that serious, maybe the altitude fried the O2 sensor? Any takes on this? Will call my SA t'row. Thanks Jimbo

 

Try the turn the key to on, back to off, 3 times thing. This may clear it.

 

SES light doesn't clear until the fault is removed or gone and goes
through several cycles. (how many cycles? not sure, neither was
the dealer as it depends on the fault, i guess).


MIL will clear after 5 restarts.
:smile:

 

went out yesterday and started the car, SES lite immediately went out. This was the third start cycle since the lite came on, so it must've reset itself, and it seems to be staying off. Methinks the sudden ascent to over 14000 ft fooled some O2 sensor or something. Jimbo

 

Same thing happen to me when I took a trip to Mammoth Ca. late winter for some snowboarding. It SES turn on at about 10,000 elevation. I cycled the system 3 times and it did NOT turn off. When I returned from the trip, I used my diagnostics adapter to check the error code. The code read something like catalyst sensor is not working at its efficiency. I had to clear the code manually. It was my O2 sensor. You might have to take it in to the dealer to clear the code.