I have this exact problem. I’m losing communication with my ECM when I’m flashing it. I did find a ground strap that is not connected to anything but the firewall. It’s only 16” at best. I think it’s part of the fuse box but I can’t find where it broke from.
2009 LMM Flashing issues
- Thread starter Misternw87
- Start date
Hood
Yup. Well back to the issue at hand. Lost communication with ECM when trying to flash it. Same with the ECBM2. Know anything about this? 2009+ LMM 6.6
My experience with that issue has been that a noisy bus is the most common cause of loss of communication in the middle of the flash. Is it happening during the programming phase or during the erase phase, or during the re-boot?
In some engine families, this firewall ground strap was attached to the back of the head. If the strap is still functional, you can attach it to the block at any convenient place. You can test the function by using a jumper cable attached to the negative battery terminal or to the block. Some trucks also have the firewall ground strap attached to the hood also. Mine doesn't, maybe yours does (or should).
What causes noise? I deleted and removed my egr. Maybe the egr ground? All those wires are just tied off to the side. My tuner did delete them so didn’t think they were too important anymore.
Unlikely. It's normally due to a module that won't shut up and sends messages during the read/write operation causing the failure. Aftermarket radios are notorious for this. But could be any of them. OnStar has been known to cause it too
Interesting. I do have on star in the truck. Is that as simple as pulling the fuse to shut radios off? I have power everywhere that needs to have power. Maybe closing doors and making all the lights turn off? I’m looking for an all ideas lol. Thanks for your time.
Yes, and yes
Does on star run off the radio as well? Or separate since it’s always on
It's a separate module under the dash behind the glovebox.
Well I got some unplugging to do. Appreciate it
The first module in the HS Canbus branch to to the TCCM and a few other modules is the VCCM, which is the module Jason is talking about. It is a common failure point on gmt900 chassis. I don't think you'll find a new one in stock anywhere, so if you find that to be your issue, or one of them, then make sure you buy a used one from a reputable source that will warranty it.
Have you tried the fuses first?
I’ve pulled some but not sure exactly sure which ones exactly. Open to suggestions.
Well while I was moving and checking things my ECM came in contact with a hot terminal. Now when I check the ECM battery fuse with my fuse light and every fuse in line with it along with my fan fuse it makes my starter relay click on off really fast and won’t start or give me a check engine light. I have accessories but no ENG power. Think I shortened my ECM. Always hot wires are hot. Any thoughts?
Moved mistern's issue out of Tim's thread, as it was starting to redirect that thread.