E38 HS canbus messages

Bosch Motronic etc ECUs and PCMs
ironduke
Posts: 579
Joined: Thu Feb 13, 2020 11:32 pm
cars: Mainly GM trucks, a Cruze and an Equinox for dailys..

Re: E38 HS canbus messages

Post by ironduke »

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.
snap
Posts: 7
Joined: Fri Nov 06, 2020 7:46 pm

Re: E38 HS canbus messages

Post by snap »

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.
User avatar
Tre-Cool
Posts: 265
Joined: Tue Oct 16, 2012 12:17 pm
cars: VY SS UTE, VX Drag Car
Location: Perth
Contact:

Re: E38 HS canbus messages

Post by Tre-Cool »

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.
snap
Posts: 7
Joined: Fri Nov 06, 2020 7:46 pm

Re: E38 HS canbus messages

Post by snap »

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.
Snoman002
Posts: 20
Joined: Tue Jul 28, 2020 12:18 pm
cars: 2005 Quadrasteer
2009 US Spec VXR8

Re: E38 HS canbus messages

Post by Snoman002 »

snap wrote:
ironduke wrote:What else do you have available besides hptuners? Do you have a gm MDI?

can you monitor a/c request with hptuners? that should change from no to yes when sending that command, that is what I am seeing with tech2win..
hptuners has the following channels that can be monitored.
  • -AC Clutch Engaged
    -AC Serial Command
    -AC Disable (WOT RPM)
    -AC Disable (Pressure)
    -AC Pressure - pressure
    -AC Pressure sensor - voltage
I have also have a VCX nano and tech2win. I'll hook it up and see what I get.

As you say, I assume the ecm is not happy with the 3 wire a/c pressure switch reading.
ironduke wrote:I am very curious if this works, seen it mentioned quite frequently as people are wanting to be cool in their swaps..
I am one of these swap people and I hope we can get to the bottom of this. Thanks for you all guidance so far.
Admittedly I am unaware of how the L77 AC compressor works but from my understanding the L76 used in the 08-09 Pontiac G8 (Commodore) does not utilize a on/off compressor clutch. Instead it is a PWM managed compressor and the clutch is always engaged. In your research I would monitor pressure and RPM; assuming a steady load on the AC system I would imagine as RPM increases the computer is demanding lower output from the compressor.
ben_att
Posts: 43
Joined: Sun Jul 10, 2022 6:44 pm
cars: VF
VZ
VY

Re: E38 HS canbus messages

Post by ben_att »

snap wrote:
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.
Did you get this working? I'm attempting something similar (except VF L77 over VE), however I've found that enabling the clutch engages the compressor clutch but there is another solenoid on the compressor which requires a fixed 12V and a negative PWM signal to control how hard the compressor is working. Without a signal to this, the compressor doesn't seem to do anything in my case, if I apply fixed 12V for testing purposes to this it works, but I don't think is is the right solution although on my 6L VZ, the compressor is always on 'full' and just 'cycles' in and out, seems like a waste having the ability to have this feature and not use it as I'm guessing when the air in the cabin running through the evaporator doesn't require as much heat exchange (or the fan is running at a low speed) it backs off the compressor which in turn I'm guessing will reduce the power lost and make it more economical (as there is a more noticeable difference in VZ economy when AC is on all the time over the VF I find). The signals are coming from a HVAC module 'K33' (attached), I might chuck a cro on the VF and run it at different loads and see if there's any obvious pattern as I can't seem to find much info about this online about what AC strength vs PWM control data is. The service manual doesn't really give much away either (attached a portion). The other annoying thing with this is that the signal is sent from a HVAC module which I don't plan on using and I doubt I can drive it from the ECU, so I will have to make up another module to control this seperately.
Attachments
AC Compressor control.pdf
(78.11 KiB) Downloaded 119 times
VF AC operation.pdf
(1.76 MiB) Downloaded 101 times
Post Reply