Re: What model ECM is this ?

[Shannen Durphey <shannen@grolen.com>]

Team ZR1 wrote:
> 
> Thanks for the reply Ludis,
> 
> The CCM is another processor that works with the ECM in the sense it controls
> functions like ABS, cruise control,
> heating, A/C, ASR, when the oil should be changed, low tire pressure, etc.
> I am told that the CCM is part of the ECM communcations package and without it the ECM
> is limited to what you can read out of it. When I turn the power switch on ( not start
> ) on a stock Corvette a light will blink a code of 1 2 to say all is well, with the
> snakeskinner, there is just a large red engine light and it does not blink at all.
> 
> John
LOL!!!  I can't believe I missed this.  Here I'm thinking it's
contained within the ECM! John, the CCM is the "Central Control
Module".  It's a separate, external box who's job is to operate the
digital instrument cluster, decode the vats signal, illuminate seat
belt, hatch ajar, and other warning lights; operate door locks and the
security system, control interior lighting, and a whole bunch more. 
It has a dedicated terminal in the ALDL (pin G) as well as two serial
data lines to communicate with the ecm, abs/tcs, and the heat and ac
controller.  I can scan this huge list of accessory functions that it
controls, if you're interested.  The CCM is also able to display
trouble codes generated by other control modules on the system, such
as the ECM and HVAC controller, through the instrument cluster.  It
coodinates data exchange between these modules, like a traffic cop. 
However, the CCM does not inhibit the scan tool data exchange.  As a
method of double checking, I'm looking over the diagnostic charts for
"no aldl data" right now, and the ccm is not a culprit in any of
them.  In addition, there's evidence that the ECM cannot tell that the
CCM is not communicating with it.  The lack of an ECM code for loss of
serial data is a big clue in my book.  

In a stock configuration, the serial data line is connected to pin M
in the ALDL, directly under A and B, so it looks like a triangle of
terminals in the right hand side, with the "ears" of the ALDL
connector positioned on the bottom.  I would make sure mine was the
same way, if I were in your shoes.  Jumpering A and B should cause the
check engine light to flash trouble codes.  Installing a stock ZR1
prom should allow Diacom communications.  Wouldn't it be nice if the
solution is that simple?

What stock vettes blink code twelve with just the key on?  Usually it
takes a jumper in the ALDL.
Shannen
PS, you've brough an interesting problem to the list.  Even the quiet
guys seem to be jumping to help.

> 
> Ludis Langens wrote:
> 
> > What's this "CCM" processor you are talking about?  If this is a stock
> > P4 class ECM, all it needs is one chip to communicate.  I can't imagine
> > the chip being desoldered to save a fraction of an ounce.  It is more
> > likely that the communications software has been removed - especially if
> > you aren't allowed to collect telemetry during a race.
> >
> > --
> > Ludis Langens                               ludis (at) cruzers (dot) com
> > Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/