i"m on cloud 9, just reprogrammed my first ECM.
 

I've been putting it off for too long. I actually bought everything I needed to start flashing about 3 years ago. I started tinkering around, and had all the programs loaded in my laptop , but nothing came into the door needing flashed for a while. I then dropped my brandy newish shop laptop, and keeled it. That pissed me off, so I threw everything in my tool box and never looked at it again.
The main reason was it was just such a time suck to set everything up. I easily had an 8 hour day on tech lines, loading all the crap back into my new laptop this week.
I had a 2004 trailblazer come in with no 4wd. I traced it down to the control module, and decided to have a go at it. The reflash was easy peasy, it was all the setup that was the killer. I was thrilled to see the switch light up, and all functions normal again. Gm uses windows 7 and you have to use an outdated versions of Java to make the programs load. I am no techie, and would have never figured this out without tech help .
I have replaced these before, and always had a workaround for having to reflash them, and have found a workaround for nearly other electronic problem I have encountered here for the last 5 years, but finally said it was time to ramp up my diagnostic chops to the next level.
I'm done updating my snap on scanner, I am going to move more towards manufacture specific scan tools from now on out. Gonna be expensive, but that's the auto biz...

Congrats Fred! A big step forward for sure, and it always feels good to pick up a new skill!

Now you will be over run with folks needing stuff flashed when they try to do it themselves and get a part from the salvage yard. It's nice to be able to do it but it can also be a pain in the hind quarters

OK, maybe I'm stupid, but let me get this straight - the ECM can prevent the vehicle from going into 4WD? That's...nuts.

The control module manages all that stuff. Engages the remainder of the drive system as required, handles the transmission, etc.
It's the way things are, these days.

Best
Les

Yeah but GM is very bad about not making sense with how they do stuff

Congratulations - I think. I find newer cars frustrating enough. Cars AND computers? I'd pull my hair out. I admire your determination to know it all. You have my greatest respect.

I'm sorry Dave, I can't do that.

The display for the AC unit crapped out on our Toyota Van. Since it also displays airbag status, it disabled those too. Toyota wanted 2k to replace the unit. These new cars are stupid complicated, and stupid expensive. Luckily I could replace the par with a salvage one for $70, but its still a scary thought!

I just got a new laptop strictly for reflash, and diagnostics. The man that takes care of this stuff for me partitioned the hard drive four ways, and he told me that nowadays, VAGCOM, Ford IDS, GM SPS, and Chrysler StarMobile/WiTech don't really like each other. The four programs on the same computer have caused problems in the past with dropped programming sessions, which can ruin a brand new, blank ECM. That'll really screw up your profit margin!

Getting the hand held scan tools, and J2534 pass-thru boxes for laptop diagnostics and reflashes are expensive, but one time-only purchases. For hand held scanners, I guess the upside on one of the tools is that it will be useful for a 20 year span. GM Tech2 will cover stuff back to OBD I years, and works on just about every GM vehicle ever made since '95. That one will pay for itself pretty quick, and pay dividends afterwards. On the other hand, Chrysler DRBIII is an expensive brick with only about a 11 year span of coverage from '96, to '07 model years that was superseded by StarMoble in '06. I bet I use mine only once every 4 months.

The subscriptions they make you buy to use the newer laptop-based stuff are really big costs for using dealer level equipment. If I didn't offset the cost with the diesel work on my commercial customers' F350's, F450's, 3500HD's, and RAM's with their exhaust fluid problems, It wouldn't be worth it to play that game anymore. They do have some options for subscriptions. You can buy a 2 day pass for programming, all the way up to annual subscriptions, with updates for your hand held scanner.