The ECM/PCM, whether new or used, must be flashed/reflashed with YOUR car's VIN by a GM dealership. The ECM/PCM calibrations are specific to THAT car.

 

So I do have a question about the computer. The dealership is telling me it impossible to use a used one.... They said you cannot flash or reprogram them period.... I’m confused because I’ve done it with other vehicles and they work fine once reprogrammed to the VIN, but these people are telling me there’s no way ...

 

Who are "they" and what type of electronics issues are you experiencing?
Does your CTS have a factory panoramic sunroof?

If yes, you want to research here:

Stop the (soaking carpet) insanity forever! - Ultraview...

Hey everyone, I think I may have figured how to keep your Ultraview roof equipped CTS bone dry regardless of the cloudburst or carwash. Earlier this Spring I was cleaning the interior of my car and heard the definite sound of stepping in water when i put my foot down behind the driver's seat...

www.cadillacforums.com

 

Who are "they" and what type of electronics issues are you experiencing?
Does your CTS have a factory panoramic sunroof?

If yes, you are want to research here:

Stop the (soaking carpet) insanity forever! - Ultraview...

Hey everyone, I think I may have figured how to keep your Ultraview roof equipped CTS bone dry regardless of the cloudburst or carwash. Earlier this Spring I was cleaning the interior of my car and heard the definite sound of stepping in water when i put my foot down behind the driver's seat...

www.cadillacforums.com

They..... is a retired Cadillac technician but he didn’t have tech 2 scanner. Only had regular code checker. All kinds of electronic issues going on and yes it has the big sunroof. Drains were clogged a while back and I cleared them and it’s been fine for 5-6 months till this started. I did just have the transmission rebuilt a couple weeks before all this stuff started.

 

It could be as simple as the fuse that supplies the 12 volts to pin 16 of the DLC under the dash that any electronic tool plugging into is blown or wiring issues, so the tool would not be functional to talk to any controller

NO, any used PCM that is for your model and year would work if it is functional and as mentioned needs your VIN # flashed in and assure the software code segments works for your vehicle
Best case is also to be sure it has the newer software updates to GM TSB corrections

This could be done by a dealer, a repair shop that has a Tech-II or someone who does PCM tuning.

 

A bad ECM is unusual, although nothing is impossible. Check fuses, corroded connectors from sunroof drain blockage, etc. as suggested before going the "bad computer" route.

 

Yes I’ve had the dang drain tube issues a while back. I’ve checked all the fuses, connectors, etc etc.

 

Are you having a problem with the car, or is the only problem the inability to link up to the PCM and check for codes?
This is more often a Ford issue in my experience and usually involves either a fuse, or possible pin dislocation in the datalink plug. If you are not able to scan for body control module (BCM) codes either I'd suspect a connection problem unless the PCM is required in order to access the BCM data.

Reprograming is not limited to the dealer. Some vendors flash the modules they sell.

 

Issues with car. Started with heater blower not coming on, then after that all the cluster went dead, now the interior lights are coming on and won’t go off and also doors won’t unlock.

 

Ok, so now I’ve checked the plugs and wires for corrosion, checked fuses, and for the past cpl days my heater blower controls haven’t been working, and blower not working but now they are working ....

 

Time to check around the engine bay for loose grounds since the tranny was dropped. There are plugs behind the panel at the end of the passenger side dash that are a hot spot for moisture related trouble and as has already been mentioned, sounds like a poor connection somewhere. I'd go back and unplug and insert all of the BCM plugs and pull the passenger side carpet back to make sure it's not damp underneath. Do this after disconnecting the battery and make sure it has a good charge.
Much of what you stated was affected is managed by the BCM.

 

Why they are called "stealerships". What they realy meant is the "options and presets" are different for every car. Each keyfob has its own presets. I suspect the preloaded options for a Premium and different than a Performance. 3.23 axle different from a 3.73. Would also be surprised if TECH2WIN could not fix (may need a subscription". Anyone know ?