IAC stopped working - Pin fried?

[tweak]

Had the idle tuned in just perfectly just to experience that yesterday the IAC solenoid just stopped working while driving, and Idle went to 2000 rpm

First checked the +12v which should drive the solenoid and found it to be absent. Connected a jumper with 12v to it and the Idle immediately went up to 3500 rpm. Then ohmed the grounding which goes through VEMS, trying the IAC lock function at minimum and maximum - No difference. No i',m wondering if i should try to move over to another pin, perhaps one of the spare ones. But it looks like this possibly also can damage the vems. Also i'm wondering where the +12V that drives the solenoid is coming from, perhaps somebody has an idea?
 
And the car yes it's an Audi S2 with the PnP Genboard 3.3, and yes i did use a shottky diod to prevent flyback.

[Jamo]

Have you checked the fuse hasn't blown in the main fuse box?

This is common on the S2, I know i've suffered it on my S2 before

[tweak]

Actually exactly this happened to me once before. A fuse was blown, but i can't remember which one it was.
I just looked at all the fuses, but could not see any broken ones. I guess a fuse would make other parts of the car fail as well..
cheers

[Jamo]

http://www.s2central.net/motronic_04_fuses_ABY.html

http://www.s2-audi.co.uk/tech_articles/electrical/engine_fuse_box.htm

Yeah it's a common fuse to a few functions, when I bought my car it was missing

[tweak]

ok, thanks
Checked what seems to be fuse 24, it was OK. Power to the socket also OK.

Had to adjust the idle manually on the throttle so the car can be driven at least. Not the biggest problem, but quite annoying.

[tweak]

That fuse description on S2central did not match my '94 S2. But did finally found a blown fuse which was correct. After changing it, the idle solenoid went to full open with RPM up to 4000. 

Then measured resistance on the pin that goes to vems to ~20Ω with ignition on. With ignition off it's close to 0Ω.

Next step was changing the INJGROUP channel that drives the solenoid to the channel that drives boost valve.
Did not connect the solenoid here, but a measurement of resistance gave exactly the same values as with the previous channel. This readings are also not affected by changing the IAC lock to full open/closed.

So.. What has blown here? Any ideas anybody? Is it the driver or something else blown inside of the vems box?

For any case measured Ω with the econoseal disconnected, it was all ok, no leakage in the wire itself so the harness seems to be OK.