Subject: Is it possible to repair the "Computer" (ICU)

[Mike Arman]

>  <mboucher70 at hotmail.com>
> To: Tony Hoffman <auditony at gmail.com>,	"quattro at audifans.com"
> 	<quattro at audifans.com>
> Subject: Is it possible to repair the "Computer" (ICU)



Maybe.

First, I'd look for a used one at a pick & pull, they usually get under $100 for them (assuming they 
don't know what it is out of and you don't tell them). Buy a bunch of low value crap, cardboard 
stiffeners, raggedy floor mats, so the "pile" you take to the register when you cash out looks like 
low value garbage.



Going into yours - In troubleshooting electrical and electronic devices, I've always found that the 
parts that work the hardest are usually the ones that break. Check for anything burnt or toasted in 
the power sections of the ECU - follow your nose, do a sniff test for toasted components or PCB 
traces. A bright light and a magnifying glass are invaluable.


I haven't been paying a lot of attention to this thread, but I think you were talking about a 
problem with no power to the ISV.

The ICU controls the ISV, but I'd be willing to bet it is through a relay somewhere - an ISV likely 
takes more current than an ECU is comfortable with. Follow the wires from the ISV to find the relay, 
test the relay (press contacts closed, see if the ISV energizes), see if there is power TO the 
relay, then follow the control wire back from the relay to the ICU. If it is OK, open the ICU and 
find what is connected to that terminal on the PCB edge connector. Look for a toasted PCB trace or a 
big power transistor - probably a surface mount device, little black rectangle somewhat larger than 
the other little black rectangles liberally scattered around the board. It will have THREE leads, 
anything with eight or more is a logic IC, not a power transistor or switching transistor.


The temp sensor talks to the ICU also, and tells it to turn the ISV on and off - make sure the temp 
sensor and wiring are also good.


The pick and pull is a good choice BUT if there is a problem in the wiring somewhere else, the new 
ICU won't work any better than the old one.

Can you borrow one to try?


Hope this helps, these are just my thoughts on this.

Best Regards,

Mike Arman
90V8Q