There really isn't any reason to use AC request over the data bus on the P01/P59 computers IMO. Might I ask why you think it would be useful when request by wire is so simple?

On the E38 or E67 the only option is over the data bus so I why you would need it on one of those computers.

 

I have been making conversion modules for the P01/P59 and E38/E67 into the BMW E46 chassis for several years now

 

I've been an auto mechanic by trade for about 25 years now and specialized in automotive electrical for the last 10-15 of those years. However none of that is really relevant to data bus conversion, even the most sophisticated scan tools never go past working with data pids, I've never seen a scan tool that would let you view the raw data in any form present on the data bus and to be honest viewing that information would be heavily frowned on in this industry. Training classes would lead techs to believe that watching the data bus with a scope attempting to track down module faults is somehow useful.....the moment you suggest plugging into the bus and just watching bus traffic for corrupted packets and you'd see every head in the room explode.

I am a self taught C++ programmer who just happens to also have a very good understanding of how electrical circuits and devices operate.

 

Nice...I don't even remember how to write a simple for/next loop lol

 

It's my understanding these PCM's use that serial request from the HVAC Module in the dash to tell the PCM to turn the compressor on instead of a 12 Volt signal wire as found in the Blue/Red harness. I've seen multiple ways to wire it like an Express Van, etc but I'd like to keep it stock with the serial data telling the compressor to come on and then let the pressure sensor, not switch, inform the PCM so as to have the PCM turn the fans on.

 

Give me a vehicle to look at, the only vehicle that comes to mind off the top of my head that uses request over serial is the trailblazer but those were P59 computers.

 

My particular application is a 2005 GMC Sierra into a 1969 Chevy truck. From what I've read I think this is common for 03-07 then GM switched to CAN and I think the CAN communicates with the A/C is similar.

 

Ok getting a bit of mixed data here. You said initially Red/Blue Pcm meaning its a 99-02 computer(P01) but now your talking about the Blue/Green computers(P59). There is a diffidence between these in terms of how AC request can be done and what over laps.

For both types of PCM's there are 3 possible configures for the AC as setup with a tuning software, its possible some programs don't give access to the AC setup but assuming they do they work as follows.

Type 1 is done as a request over the data bus and system pressure is monitored with a pressure transducer. May also use a low pressure cut out switch to disable AC.
Type 2 is done as a hard wired request and uses a pressure transducer to monitor line pressure. May also use a low pressure cut out switch to disable AC.
Type 3 is done as a hard wired request but uses a pressure cycling switch on the lower pressure side with a pressure cut out switch to disable the system on the high pressure line.

All P01 computers can be setup to work with all 3 methods above.
All P59's that are capable of controlling an IAC for drive by cable throttle can also be setup to work with all 3 system types listed above.
P59's that are not capable of drive by wire throttle will work with AC Type 1 or Type 3 only.

AC System Type 1 & 2 will control a multi speed fan based on system pressure read by the transducer, vehicle cooling fan control based on engine temperature will work for low speed fan and high speed fan with the ability to control AC inhibit based on min and max temperature values.

Type 3 allows fan control for high and low speed fan control based on engine temperature and also allows for either high or low speed fan engagement based on Ac request outside of temperature based fan control. You can also configure the High and low speed fans to run based on vehicle speed over X mph and when vehicle speed falls below X mph.

I think I've only ever had one other person who asked about AC request over serial data but it was with an E40 from a Trail Blazer where the PCM has both CAN and J-1850 data buses in use with no option for a hard wired AC request.

Designing something that reads a switch and then sends a message over the data bus is possible but unless your developing something like that for personal use just to say that you did it seems rather pointless when there are much simpler ways to do the same thing with just a switch.

 

Thanks for the info. Mine is a Drive By Wire and has the pressure transducer and low pressure cut out

 

Thanks for the response.

 

Well I glad you're here on LS1tech. Great job.

 

For anyone wondering.....this is far from a dead subject. I've been working on this pretty diligently while I've been off work due to the COVID-19 quarantine in my state. I'm just about happy with the hardware at this point and have worked out the issues with an end user being able to "update" the vin number in the module and set the way the module collects and passes data from the engine computer to the Jeeps data bus. About the only real thing I'm still working on gettting sorted out is software that will allow for firmware updates on the modules main program.

 

That is great to here!!!

 

PeteS160

Hey man this is awesome. I’m needing one for my Jeep. Have you decided to sell them yet?

 

What type of Jeep....and what year. Also what type of PCM?

 

I see an STM32F103 on there (actually 3), have you considered OpenBLT as a bootloader to allow the main application to be updated? https://www.feaser.com/openblt/doku.php

its GPLv3 but there is a commercial license available if you'd like to keep the project closed source.

 

PeteS160,

Mine is a 2003 Jeep Liberty 4x4, running 11.5” lift, on 37’s, but gonna change that to 40’s. I’ve got 1 tons front and back. I’m gonna need something with some freaking pep do to the big meats on it.

 

Hey Pete if you are making your processor for purchase now I would like to buy one . I have a 03 jeep liberty. I'm putting a 5.3 with a 4l60e in it . I have complete donor vehicle. Right now it has 31 with 3 in lift ... looking to do a sfa swap after the engine swap . I appreciate your time and hope to hear from ya .

 

Just want to add that the Liberty has to be one of the best sleepers. Even the stock wheels and ride height hide the fact of the engine swap.
Very nice work on figuring out the conversion box to get the two computers to be able to talk with each other and have the dash and other body module functions working.

 

Just noticed there are a few new posts....while I haven't had a lot of time to get much done on the Liberty this year my planned upgrades are coming along slowly.

I've got the 2 1/2 inch drop on it now.......I also have the 9 way adjustable valving struts and shocks on it as well.
Rear suspension has been addressed and I've switched to the Iron Rock upper control arm using a 1 1/2 inch flex joint rather then the stock style ball-joint.....
Rear low control arms have been upgraded to thick wall square stock arms with an improved bushing design....
I still have to do some work on the fuel system before I can even drive it now.....the rear control arm interferes with the corvette filter/regulator I have on it and it's probably a good thing since the fuel pump I put in over the winter was over powering the regulator inside the filer pretty bad.

New wheels/tires are on it.....wheels are 17x9 inch Riddler's and I was able to get a 255/55 tire on it with only slight rubbing on full lock turns. Tires are rated for 149 Mph and are made from a rather soft(sticky) compound and should help the Jeep hook up so it stops blowing the rear tires off it