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Its been a year since I bought a BCM to try to get cruise and AC working in my E38 controlled LS7 swap. That failed miserably when I realized that I had to then buy each individual module from the factory GM interior to make things work. BCM got sold right back on ebay to someone else. I went on a detour for a year playing with other cars, though am coming back to my Rx7 now to see if I can finish off some of the remaining things, like AC and Cruise. I decided to poke around on google and see if anyone had figured out the canbus stuff by now for AC. To my surprise, I found something made by a site called rpmextreme. Has anyone used this? Is it the answer to my prayers? http://www.rpmextreme.com/Product/23...st-Module.aspx
It kind of reads like I can wire it into my harness (hopefully not into my OBD2 connector... that might make hooking up HPtuners not work??) and then just request AC just like I could in the old LS1 PCMs and let the PCM control it. Anyone with experience? I searched in this forum to see but didnt come up with much in regards to matches.
I have no experience with it, but it sounds promising. Says you can either plug it into the OBD port or hardwire it. It is a little pricey for just AC, but I guess if it works and you're dead set on having the ECM control the AC it may be worth it.
I have no experience with it, but it sounds promising. Says you can either plug it into the OBD port or hardwire it. It is a little pricey for just AC, but I guess if it works and you're dead set on having the ECM control the AC it may be worth it.
It is vastly overpriced for what it does. It is a cheap microcontroller($5 kind of cheap) in a relay housing that just sends the correct message over the CAN bus.
I just bought the HVAC/radio controls from a Camaro off eBay and will put it on my test bench when it gets here. That way I can get the CAN bus message it is sending to the ECM. I need to do this for my swap anyway. It is winter so I have been putting it off.
as far as i know, there are no micros for $5 that can directly interface with the can(if there is, please share). it requires a few more chips, but its still probably about $20 worth.
but the real question is, can you make them for $250 worth of your time, energy and parts?
as far as i know, there are no micros for $5 that can directly interface with the can(if there is, please share). it requires a few more chips, but its still probably about $20 worth.
but the real question is, can you make them for $250 worth of your time, energy and parts?
ESP32-WROOM-32 - You get CAN, WiFi, and Bluetooth. $3.90 for a single on Mouser. My $5 cost refers to the cost of the MCU only.
I agree with crash. This is something I've been interested in but not for $250.00 I'm working with a 2005 that uses the serial data line. I'm planning on getting the HVAC module out of a comparable donor truck and going that route
I agree with crash. This is something I've been interested in but not for $250.00 I'm working with a 2005 that uses the serial data line. I'm planning on getting the HVAC module out of a comparable donor truck and going that route
Yeah, when I saw what they were selling for $250 I decided that it was time to most of it myself. I integrated the BCM from the donor vehicle for my swap.
The HVAC/radio control panel I ordered arrives later today and I will start probing it this weekend along with some other CAN bus reverse engineering.
If I understand my setup correctly the 2005 PCM uses serial data to communicate. I think I read that GM switched to CAN-BUS in maybe 2007? Looking at different wiring diagrams for my application I think the HVAC communicates directly with the PCM and not through the BCM. The Tunner that removed the VAT's, etc. from my PCM said he's had other people asking him about this issue and if he ever get's time he wants to do exactly what you're planing on doing. Again I think there is a real interest in this issue and I look forward to following your progress.
Well I purchased a HVAC Module from a 2005 Chevy Avlanche and did some probing on it. Using the dash harness I got from my donor vehicle i put 12 volts to the orange wire, pin B7, tied the Black & Black/White Grounds, Pin B9 & A8 respectively and I see 2 Volts on the White Serial Data line Pin B11. If i were to wire this up in the truck do you think this would be sending the correct request to the PCM to let it know the A/C is on? By the way neither the A/C butoon light or any other lights came on the Module. I'm going to try to attach the Wiring pin out for the Module.
It is vastly overpriced for what it does. It is a cheap microcontroller($5 kind of cheap) in a relay housing that just sends the correct message over the CAN bus.
Its way more involved than a cheap micro controller inside of a relay housing. The unit is housed in a IP-53 9 pin housing and the canbus interface is ISO 11898-2 compliant. It is designed from the ground up to be used in industrial and automotive applications.
We have the ability to program it for many different functions and to be able to use the multiple inputs and outputs for different applications.
We originally figured all the canbus applications out with a larger module that we use with our Jeep LS-LT conversion. Now we are creating "solutions" for GM LS-LT GEN4 GEN5 standalone applications using the smaller modules that can be used for things like AC request, TAP SHIFT, TOW/HAUL, PWM FAN CONTROL, REVERSE LAMPS, ETC.....
All of these "solutions" are based on a swap that is not running a GM BCM. We send the messages that the BCM would have to signal the ECU-TCM.
If you have ideas for an application that we do not have listed, feel free to let me know and I will see if its something that we can do.
Do you currently offer or plan to offer a can bus module that would output analog signals for gen iv/v swaps into earlier gm vehicles(gmt400, 3rd and 4th gen F bodies. etc) to retain factory gauges? Speedo, Tach, Coolant temp, and oil pressure.
Originally Posted by Rpmextreme
Its way more involved than a cheap micro controller inside of a relay housing. The unit is housed in a IP-53 9 pin housing and the canbus interface is ISO 11898-2 compliant. It is designed from the ground up to be used in industrial and automotive applications.
We have the ability to program it for many different functions and to be able to use the multiple inputs and outputs for different applications.
We originally figured all the canbus applications out with a larger module that we use with our Jeep LS-LT conversion. Now we are creating "solutions" for GM LS-LT GEN4 GEN5 standalone applications using the smaller modules that can be used for things like AC request, TAP SHIFT, TOW/HAUL, PWM FAN CONTROL, REVERSE LAMPS, ETC.....
All of these "solutions" are based on a swap that is not running a GM BCM. We send the messages that the BCM would have to signal the ECU-TCM.
If you have ideas for an application that we do not have listed, feel free to let me know and I will see if its something that we can do.
Do you currently offer or plan to offer a can bus module that would output analog signals for gen iv/v swaps into earlier gm vehicles(gmt400, 3rd and 4th gen F bodies. etc) to retain factory gauges? Speedo, Tach, Coolant temp, and oil pressure.
No. I don't think that is something I could do. I can use canbus messages to activate outputs with either 12 volts , ground or PWM but I can not send variable analog signals.
For coolant temp the engine computer uses two different range pulldown resistors. when its cold it uses one resistance value and when it gets closer to operating temp it switches to a different resistor for more accuracy.
For the Tach you may be able to use the Tach output from the E38 to run your tach in the dash. you may need a pull up or down resistor.
Or I think a E40 ECU has canbus and serial data and can run a GEN4 LS engine.
It is vastly overpriced for what it does. It is a cheap microcontroller($5 kind of cheap) in a relay housing that just sends the correct message over the CAN bus.
I just bought the HVAC/radio controls from a Camaro off eBay and will put it on my test bench when it gets here. That way I can get the CAN bus message it is sending to the ECM. I need to do this for my swap anyway. It is winter so I have been putting it off.
Its good to see this is back up, I had a post asking a somewhat similar question for the Gen V. Ideally I would like cruise, tap shift, and AC, I was also focused on getting the original dash to work to use for a while. Everything gets expensive and thought it would be a good option.
I have seen some others with the CAN bus plug modules, there may not be another way around this.
Thanks
Dave
Not OP, but I've emailed RPM Extreme three-ish times with questions and attempts to make an order and have never received a response. Admittedly, I haven't called yet.
Swaptime has one as well it has quite a few more features but is a bit more pricey. It is their "Muscle Car Module". It seems GM has the CAN bus locked down to a degree without using all the extra GM switches. To make a fun driver it is nice to have all the extras but those come with some added pain.
Dave
if I’m not supposed to drop names please delete them. I’m not sure they are sponsors
Last edited by custom 68; Feb 17, 2026 at 06:14 PM.
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RPM Extreme AC Request module? 
