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[mongocanfly]

The ecm doesn't have anything to do with lighting..at least not on mine..mine are 02-03 engines

[nsb29]

Originally Posted by mongocanfly

The ecm doesn't have anything to do with lighting..at least not on mine..mine are 02-03 engines

Kipp brought it up in post 16 I have also read this in other posts where people were having a problem with torque converter lock up using LED lighting, at the moment I don’t plan on using LEDs. He also brought up that the ECM may want to see grounding when the brake pedal wasn’t pressed. Just figured if I’m trying to get my head around all this I might as well ask all my questions at once lol

[ls1nova71]

It's the same thing as cruise control on GenIIIs, if you run LEDs the cruise wont set. The PCM needs to see the ground path through the brake lights, the 3rd brake light on factory applications. As long as you have at least one brake light or a relay to provide that, it will work. It "sees" the ground through the filament in the brake light as long as its hooked to the normally open side of the brake switch. How it actually works is really irrelevant as long as you know it needs to have it.

[mongocanfly]

I dont have torque converter or cruise control....guess that's why it's not a issue on mine...but I didnt know the ecm had anything to do with running leds...

[ls1nova71]

Originally Posted by mongocanfly

..but I didnt know the ecm had anything to do with running leds...

It doesnt really have anything to do with running LEDs, but just wont function correctly with LED taillights.

[nsb29]

Well I want to thank all of you for your help, next is to gather up the parts I need and see if I can stick it all together and of course have it work Hope y’all had a good Christmas

[nsb29]

Well I thought I was out of questions, my son brought up the fact that with some manufacturers you need the BCM that went to the donor car or have the replacement recalibrated. Hopefully that only pertain to the Rice grinders he works on lol

[kipps]

Originally Posted by nsb29

Well I thought I was out of questions, my son brought up the fact that with some manufacturers you need the BCM that went to the donor car or have the replacement recalibrated. Hopefully that only pertain to the Rice grinders he works on lol

That's been a bit of an unknown for me too. I'm starting out with a truck engine and ECM. I'm reflashing the truck ECM to a Camaro tune for more guaranteed manual transmission compatibility. To avoid any chances of trouble with the BCM/ECM mismatch, I purchased a manual trans Camaro BCM, and will reflash my ECM to the same VIN. This should give me a matched set.

I've heard of some mismatching of the the BCM being okay. Since you will be deleting VATS, the BCM doesn't need to be a perfect match with the ECM to allow the vehicle to start. Also, you're likely not even running the start circuit through the BCM anyway. I'm not.

Some folks who've used the BCM for cruise, charging, and other simple stuff, say there's no problem using a mismatched BCM for the purpose. I think they all grabbed one from the same type of vehicle, though. I figured it was hoping a bit much to get a camaro ECM and a truck BCM to work together, which is why I wanted that matched set.

When I get things running, I may try tossing the truck BCM into the mix, and see if it works. I won't know for another month or two, though.

Edit to add: all that is a long way to say, that it's definitely best if you can find the BCM from your engine donor. Failing that, pull the BCM from a similar year and similiarly equipped G8. If, once everything is assembled, and the BCM and ECM don't like each other, have a dealer do a ECM reflash to match the BCM VIN. It appears the ECM's are more cross-compatible when reflashing then the BCM's are.