I have a friend who is contemplating getting a blank ECM for his 2009 Sierra 1500 5.3L (let's just say my friend knows somebody who can get him this "swap-only" GM part...)

He is considering sending it to a tuner, then putting it in his truck, keeping the stock ECM in case he needs to take the truck in for service.

His concern is about the Big Brother called OnStar. He knows that OnStar communicates with the ECM, and routinely transmits DTC info to the Government Motors servers. The question is:

Will putting a new ECM in be detected by the OnStar system? Does the ECM have a serial number that is uploaded? Or is the VIN (which is flashed into the tuned ECM) the only identifier that OnStar uses?

My friend thanks you in advance.

I get Onstar diagnostic notifications every month with no issues and I have swapped my ECM several times. When I had my Edge Evo pile of crap handheld, the Onstar diagnostics got hosed up, but since I dumped that POS and got a real tune, it has been working fine and "Big Brother" has not picked on me at all.

No onstar will not know. The friend is you isn't it

No, nyet, nein, non, nope...uhn-uhn. Not me at all....

Yeah, sure.

Here's what I've learned. (Learn from my mistake....)

If you install a new ECM tuned with different tables, and you get a "Check Engine" light, and you push the little blue "OnStar" button and ask them to diagnose the light...

...you're screwed. You have just transmitted checksums that show them (and GM) that you either swapped the ECM out or got the OEM module flashed with new tables.

So the answer to my question is, "YES, ONSTAR KNOWS WHEN YOU'VE INSTALLED A NEW ECM..."

Now, when (my friend) takes his truck in for powertrain warranty work, the dealer will be able to laugh in (his) face...

Moral of the story (one I wished I'd known...) is that you should call OnStar and opt out of the diagnostic evaluation program. They can't (legally) download your ECM data then. Whether they still will is anyone's guess...

I solved this whole issue by pulling the fuse for OnStar and when I get around to it, the module will be doing the same thing that the XM module is doing, sitting on the shelf. Well, technically the XM module is still sitting in the back of the truck and has been for 4 or 5 months because I've been too lazy to take it in.

I agree hell with onstar but XM man ur crazy i love it

I like metal and XM's metal stations are pretty soft, Metallica is typically their hardest stuff. And I don't want to screw with paying some company to listen to commercials in a "commercial free" radio. "but we have over 50 channels without commercials" "and you have 150 channels, 2/3 of your channels have plenty of commercials" That's pretty much how the conversation started with the XM rep. All the commercial free stations are Britney Spears and nSync and whoever the hell else people are listening to now-a-days.

Totally aggree brims....I'm a metal head too....and while Metallica is cool and all.....its just not enough....so screw the XM/Sirius iPod it is. That way you can listen to commercial free music and play any song you want to....oh and other than the cost of the iPod...its free.