E38 HS canbus messages

Bosch Motronic etc ECUs and PCMs
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Joined: Thu Feb 13, 2020 11:32 pm

Re: E38 HS canbus messages

Postby ironduke » Wed Nov 11, 2020 1:26 pm

I didn't think/know you were using the BCM.. This might throw a wrench in the works for the a/c request but I'm not sure..

When monitoring the bus there is the ac request=no messages and then there are the a/c request=yes messages.. Can you monitor your high speed bus for these messages? With no a/c control head I do not know if the BCM is still going to send the ac request messages or if those messages will be silent.

If your using the BCM it may be a better idea to build a little low speed canbus device and use messages from the gmlan bible to request a/c on the low speed which the BCM would see and then forward onto the high speed bus..

Honestly not sure which way is better, for me it would depend on if the BCM is sending ac request=off messages all by itself with no ac control head present..

What is your layout? Matching ECM/TCM/BCM? Same year and everything?? you using anything else? IPC?

For the backup lights to work there might be something else missing? or a different message that is also sent for reverse? If you get tech2win working try looking at the BCM input data list and see if reverse is listed, might help ya nail that problem down.

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Joined: Fri Nov 06, 2020 7:46 pm

Re: E38 HS canbus messages

Postby snap » Fri Nov 13, 2020 8:30 am

ironduke wrote:I didn't think/know you were using the BCM.. This might throw a wrench in the works for the a/c request but I'm not sure..


I have the BCM but not sure if I want to run it as I cant seem to get the things I want from it: I was hoping to get reverse lights, ac request, tutd, cruise and variable charging. Charging with battery current monitor is working but nothing else vua the BCM. I think I will keep the BCM running on the bus and slowly work out each of the items.

ironduke wrote:When monitoring the bus there is the ac request=no messages and then there are the a/c request=yes messages.. Can you monitor your high speed bus for these messages? With no a/c control head I do not know if the BCM is still going to send the ac request messages or if those messages will be silent.


I'll take another look and report back.

ironduke wrote:What is your layout? Matching ECM/TCM/BCM? Same year and everything?? you using anything else? IPC?


ECM/TCM/BCM are all from the donor vehicle - no IPC. To add to the mix is PIM which controls the gauges of the vehicle receiving the transplant GM Holden Rodeo - haven't got this working either (feeling like I would need to build a gateway/translator for this to work).

ironduke wrote:For the backup lights to work there might be something else missing? or a different message that is also sent for reverse? If you get tech2win working try looking at the BCM input data list and see if reverse is listed, might help ya nail that problem down.


I have managed to get reverse lights working by using an arduino/canbus shield and listening for the PRNDL shifter message. Then I send the device control message to turn on the reverse lights (with keep tester present message). It works but not the ideal/correct way of doing it.

I also did spend a bit of time isolating the messages each of the ecu's (ECM/TCM/BCM/PIM) so now I know which messages to target/ignore.

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Location: Perth

Re: E38 HS canbus messages

Postby Tre-Cool » Sat Nov 21, 2020 12:16 am

has anyone worked out how to change the throttle mapping?

the e38 has 3 throttle maps, generally they are pretty similar if not same if most tunes, but i'd like to be able to really limit the default map, then change it to adjust power levels.

car is supercharged & makes 900whp & i already use the standard mapping to stop the throttle blade from opening 100% till 5000rpm at wot, and dulled it immensely at light pedal movements.

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Joined: Fri Nov 06, 2020 7:46 pm

Re: E38 HS canbus messages

Postby snap » Fri Nov 27, 2020 5:44 pm

ironduke wrote:1A1 looks promising.. I think it's more A/c clutch applied/A/c clutch not applied, not the request your looking for..


I can confirm the 1A1 messages are the status for the "A/C Clutch Engaged" (on or off)
1A1 - 00200000 = status on
1A1 - 00300000 = status on (when on via scan tool)
1A1 - 00000000 = off

ironduke wrote:1F1AE1600000800007A << this turns the ac clutch on in the suburban..
1F1AE0E00000800007A << this seems to turn it off.. or if it stops seeing the message above after a couple seconds..


The 1F1 is the "AC Serial Command". When I repeatedly send the: 1F1 AE1600000800007A command the scanners show that the "AC Serial Command" is on.

because my system isn't gased yet, the "AC Disable (Pressure)" is on and I assume this is stopping the AC Clutch from engaging (1A1 message above).

I'll get me system gasesed and see if this works as expected (I suspect it will) and I'll report back.

Thanks for the help so far.

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