RE: CIS Light Comes On

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

> 	> > Would an '84 5kS non-t have any way to get at fault codes in teh
> ECU?
> 	> > 
> 	> ... I think that on your car there is a diagnostic mode, and it
> uses the
> 	> tach to feed back the codes.  If you have a Bentley it should tell
> you ...
> 	> if not and you don't hear from anyone else with the details let me
> know and
> 	> I can look it up ...
> 
> 	No I don't;  it would be most helpful if you could look it up,
> 	as I've asked previously and teh only answers were roughly 
> 	"I think it's something with the tach", but I could never
> 	get details.
> 
> ... I'm just going from a recollection of what my brother-in-law told me.
> As you know, he too has an '84 5kS.  I know I looked something up for
> someone and found that there was no such diagnostic, but I'm pretty sure
> it was for a different car.  I'm copying the home e-mail account as a
> reminder to me ... I'll let you know what I find!
> 
I thought I'd pass along the results of my investigation to the list as well
... I sat down with a couple different Bentley manuals to find out which car
has what system.  Based upon what Bentley says and the wiring diagram for
the car, there is no built-in diagnostic capability for the non-turbocharged
versions of the '84 5000.  The car that uses the tach to provide diagnostic
feedback is the turbocharged '84-85 5000 with the KH engine.  The diagnostic
is activated by switching on the WOT switch while the car is idling (or
stopped with the ignition on after a failure to start).  The "check engine"
light and the tach value are used to indicate what failure was identified by
the ECU.  I know that my BiL has never owned an Audi turbo, so I need to
find out from him which car had this diagnostic capability.  

In any event there is a troubleshooting procedure for the '84 5kS in the
Bentley which looks pretty thorough, so just because the ECU can't give you
codes doesn't mean that you won't be able to figure out the problem.  I wish
I would have had this message with me when I was reading the Bentley as I
could have seen what it had to say about what conditions cause the "CIS
Light" to be illuminated.  I s'pose I could just go back and look it up
tonight ...

HTH!
Steve Buchholz
San Jose, CA (USA)