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Old 11-17-2008, 09:37 PM
Roncallo Roncallo is offline
88Black560SL
 
Join Date: Oct 2004
Location: CT
Posts: 3,510
Quote:
Originally Posted by whipplem104 View Post
Actually once you get a speed input for the tcu thats all you need. The tcu has a programable output for the speed output. I am using a stock 400e speedo which uses a the same input as the sl.
Yes you are correct that you need a speed sensor either the abs sensor or one on the driveshaft or wheel speed. Any configuration can be used as it is just programmed.
The problem with the CAN is that you also need to send messages back to the other control units. This is the reason you could not just stick a old style trans or a stick shift in. The rest of the computers would go into limp mode. Also mercedes loves to change this stuff from year to year and car to car as they do updates. The demand is never going to be there for PCS to do this for the mercedes. My hope is that we can get the internal speed sensors set up for proper gear recognition and the additional controls that will give.
It looked to me like you could use N2 and N3 and get away with it but wheel speed and engine speed are also needed to get the accurate picture.

I understand PCS's dilemma but I would think things like engine speed, wheel speed and throttle position are very basic. I would think these would stay the same, but then MB might change them just to piss us reverse engineers off. I did find some CAN bus reverse engineering software that would crack the CAN code in a heart beat but it's $5000.00

As far as sending messages back to the other control units I am aware that it does that, but I'm not to certain of the outcome of things if they dont get the signal. I had my ETC disconnected and the car seemed to start and run fine at least in park. There was no indication of the engine being in limp home mode. The ETC for the 722.6 sends out the following signals to the rest of the car over the CAN.

Conversion (internal torque calculation)
Engaged gear
TC lockup status
Transmission overload protection requirement
Kickdown
Limp home mode.
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