[V8] Tranny ECU nothing comes back when attempting to pull co des

Buchholz, Steven Steven.Buchholz at kla-tencor.com
Thu Mar 4 21:53:16 EST 2004

... to answer your question ... the tranny ECU (TCU) is pretty doggone
simple to replace ... it is mounted above the brake pedal, behind a cover in
the driver's footwell.  

So ... was your transmission working well when you brought it in?  Was the
PRNDL display on the IC working as you moved the shifter?  If so, I'd be
surprised if the TCU was really dead ... the connection to the diagnostic
connectors is screwed up (as it is on my car after the connectors sat
submerged in water) ... or perhaps the technician didn't carefully follow
the directions for reading codes out of the TCU.  This is precisely why I
would not trust my car to anyone ... especially not dealers!

The tech is correct in that the TCU does supply power to the cruise control,
and if it is detecting a problem it will not allow the CC to get power ...
but in that case you would see the PRNDL display not working.  Now that I'm
thinking about it I'm pretty sure you can read diagnostic codes out via the
PRNDL display.  

Do all the standard troubleshooting first ... make sure that the switches on
the brake pedal are *ALL* working ... the CC requires that the vacuum
switch, its electrical component AND the brake light switch all are
functional.  If you have an electrical problem that makes your brake lights
inoperable that can cause the CC to not work.  On my car I found that it was
the power switch on the column that was preventing operation of the CC.
Make sure you go through all the simpler and cheaper alternatives before
targeting the TCU ... 

For some reason or other (actually, I was looking into "chipping" the AT box
... OMG!!!) I've collected a couple TCUs over the years.  My cars don't need
'em, so if you find you need to borrow one don't hesitate to ask.  That
said, I'm a bit hesitant to loan out anything because in most cases it takes
work to get it back ... 

Steve B
San Jose, Kaleefohnia (USA)
> Help! My mechanic is telling me my tranny ecu is dead. All of 
> this trouble just because I want a working cruise control. 
> Anyway, does anyone have any idea where I can find one? How 
> difficult is the tranny ecu to replace?

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