Page 1 of 1

5HP CAN bus transmission control

Posted: Thu Aug 04, 2022 10:48 pm
by AndreyB
Just made an early year 1995 BMW 750 v12 e38 friend in NJ - mine is "mk2 m73n/m73tu" his is just the orignal M73, the one with dual 88 pin ECU control.

He is 5HP-curious, looks like that early 90s vehicle is already fully CAN-bus transmission integration? We've made a mild attempt to hook to the CAN bus with no success.

Open question what baud rate is M73 CAN bus. Open question if we know anything about packet payload.
image.png
image.png (968.06 KiB) Viewed 2848 times
image.png
image.png (726.82 KiB) Viewed 2848 times

Re: 5HP CAN bus transmission control

Posted: Thu Aug 04, 2022 11:03 pm
by AndreyB
Weird

on the one hand some documents claim only TU models to have CAN but I've seen the CAN bus star connector with my own eyes
image.png
image.png (59.95 KiB) Viewed 2846 times
image.png
image.png (14.76 KiB) Viewed 2846 times
image.png
image.png (78.99 KiB) Viewed 2845 times

Re: 5HP CAN bus transmission control

Posted: Thu Aug 04, 2022 11:06 pm
by AndreyB
https://www.bimmerforums.com/forum/showthread.php?1681783-CANBUS-Baud-rate-E39&p=25000930#post25000930 is the winner - they claim 100kB

Well, weird, I've tried that :(
image.png
image.png (153.01 KiB) Viewed 2844 times

Re: 5HP CAN bus transmission control

Posted: Sat Aug 06, 2022 12:28 pm
by Zeiss
Hey Andrey,

I will try to bring some light into the darkness. :)

So, first of all: 5HP is in every BMW (BMW called this gearbox A5S....., i.e. A5S560Z for 5HP with 560Nm) a CAN controlled gearbox, always and every time. 4hp (used with M70 i.e.) is always "digital controlled", GPIOs and PWM signals. So, we hold, 5HP is always CAN controlled.

Then, CAN-Bus in E38 is quite small, only DME (DME 1 and DME 2 from M73 or DME 1 from M62), AGS (Transmission Control Unit), Instrument Cluster, ASC/DSC (Dynamic Stabilization Control) and EML (if present, like by M73) communicates over CAN Bus.

Here you can the topology:
image.png
image.png (96.58 KiB) Viewed 2772 times
Anyways, it is CAN HighSpeed. The speed, I don't know, could not find anything now in a hurry, but I'll look for it again later and let you know.

EDIT SAYS:
I found out, that BMW uses just two transfer rates on CAN: 100kbit/s and 500kbit/s. So, I would say: try it out :)

Re: 5HP CAN bus transmission control

Posted: Sat Aug 06, 2022 9:03 pm
by AndreyB
Fun status update: said 5HP vehicle is lightly armored and has two starters just in case.