pcmhacking.net

Have been a long time viewer for the invaluable info I get from this awesome site. I have a VX Berlina LS1 donor car with the engine/trans and full loom assembly being transplanted into a old Chevy. I’ve searched and don’t seem to find any real answers. From the loom I have deleted the abs, airbag, power windows, radio etc. I will be using the BCM(LUX) as the wiring in the old car is very poor.
From what I read the serial data bus line will get me into trouble (any suggestions??). Having the airbag and abs module “disconnected” technically should make the car run. After deleting all the un-necessary stuff, I tested all functions of the loom with the cluster still connected – lights, indicators etc and start relay, fuel pump relay which all seems to do its job. I also tested this without the cluster connected and still ok. I had the PCM’s VATS removed but later found out the BCM still needs the key to allow the fuel pump relay work, so I’ve decided to hard wire the key to the ignition ring wire and use an immobilizer with it.
The loom has only been ran on the bench so far and is yet to be installed into the car. One problem I can see it using the BCM to activate an aftermarket air conditioner. The main reason for this is to allow the engine to increase its revs while the ac pump is on & run the fans. If I had a low level BCM I could just apply 12 volts to the pin 9 of the BCM AC select wire – see pictures. But having ECC, the serial data bus takes in effect for the AC operation.
Does anyone have any ideas to overcome this? Or do I run a separate relay circuit to the pump.
Another question is I’m wanting to retain the cruise control/throttle cables as im using the commodores brake booster and pedal assembly. I see the cruise module talks to the throttle relaxer & ABS via SDI. Will this also work?
I thank you for any input.
Cheers,
Matt

The serial is aldl data. The pcm is vpw. You must have kept the pim. That module translates the vpw to aldl to bridge the pcm and the rest of the platform.

Thank you Antus for replying. I've looked into a BCM simulator mainly for the aldl air-conditioner control, but can see they don't work with LS1 PCM/PIM.
I have basically mirrored the full loom and kept all needed modules eg. PIM.
Can you suggest a way of using the aldl bus to activate eg. aftermarket Sanden AC pump? Apoligies in advance for my naivety.
Thank you.

To allow an aftermarket air-con to control the engine's IAC and A/C compressor, you would need to send to the ALDL bus the appropriate message(s) that the factory EEC unit would have done when it was installed in the donor VX Berlina.

As described in the Gen III V8 Engine Management manual, the BCM acts as a bus master that periodically polls the various modules for their current status. When the ECC (as installed in the VX) is polled, I'd expect any change in its current state - such as the press of the A/C switch - to be placed onto the bus as a status message, which could then be monitored by an ALDL bus sniffer in real time.

This would allow identification of the ECC message and any changes therein, coincident with what was being commanded at the time. Once the unique messages are known, one could then custom program a PIC or similar micro device to send the appropriate message when polled by the BCM and in response to a hardware signal from an aftermarket air conditioner as fitted to your Chevy.

Everything I've suggested here is pretty standard stuff, but it's not based on any actual experience I've had with an ECC. I've used such methods though, when designing with PICs to monitor and control various other parameters via ALDL and/or VPW on both VR and VZ models.

Unfortunately, I don't have access to a VX with ECC that I can check, only a VZ SV8 with the standard A/C.

Thinking further to overcome this issue, I can buy eg. Ebay BCM with key = would I be better off to swap the bcm with a lower level eg. mid/low that has manual HVAC manual controls and just apply the 12 volts to BMC AC select pin(9). Current BCM is LUX 314.
If so does the loom plugs still fit? Or I chop any plug(s) from a wrecker. If anyone can confirm. The PCM has vats removed, therefore no need to link BCM to PCM. Replacing the BCM with lower type would be cheap and less headache.