I really need help with this one. My sister has a 2005 Cadillac CTS 3.6 . The car has a some issues but nothing major. Lately the car has thrown some random codes and was running rough. I went to move her car and when I went to remove key it wouldn't come out . I ordered a pcm and had it programmed and still is doing the same thing. Something else I noticed was all the windows stopped working and it takes awhile for the radio to kick on. The car starts right up and runs fine from what I can tell. I was thinking it was the BCM but I'm not sure. What do you guys think. I checked all the fuses and nothing is blown. The windows stopped working before the new pcm and still after. Main issue key stuck in the ignition, windows don't work, service theft system message, radio takes awhile to work..
The key cycle was done . Battery voltage is good same with charging voltage..Really hope someone can help me out...
As for the "why" those components aren't working right it would be helpful if you remember what "random codes" were being set. Specifically if there were any Communication/Data Link codes. "U" codes
The thing that the power windows, theft module, and radio have in common is that they're all on the Class 2 Serial Data Bus so that's probably a good place to start your troubleshooting.
If you've never troubleshooted a communication network before this isn't a bad start because it's a "single wire" network. One single wire goes to all of the modules on the network. All the modules on the Class 2 Data network "talk" over that single wire.
They "talk" using variable pulse width modulation of 0 to around 7.5 volts and if you hooked up a scope to that wire, as the modules "talked" it would look like this:
The pointer on the bottom is showing where one module was done "talking" (voltage stayed at 0) and another module took over the network bus (wire) and started "talking". Only 1 module can "talk" at a time but all this stuff is happening really fast.
As far as troubleshooting, ideally you'd use a bidirectional scanner and "auto scan" all of the modules and see if the scanner could communicate with all (or any) of the modules on the Class 2 Data Bus. But most guys don't have a scanner that can do that because they cost too much.
However, if you have access to a good scanner, and it CAN communicate with the modules but the ECM can't, you'd start checking the C2 connector on the ECM for the Power inputs and also the Class 2 Data Link pin connection on that C2 connection to the ECM.
So you got me thinking, how can a guy without a high dollar scanner start to troubleshoot this? There's no free way to do it. At the very least you'll need a 1 channel digital scope like a uScope ($180) and a multimeter.
You could observe the Class 2 Data Bus voltage square wave using the scope. Your DLC connector looks like this and you can access the Class 2 bus on pin 2.
The thing about the radio taking a while to work (but finally does) makes me think that this network is either being (intermittently but mostly) pulled down and stuck on 0 volts. Won't be a square wave, it will be flatlined at 0 (short in the wire or a module). Or being "held up" on 7 volts. In this case flatlined at 7+ volts (faulty module). Both will keep the other modules from being able to communicate .
Needless to say if you want to troubleshoot this put in a few hours of watching youtubes on the GM Class 2 Network.
The only other thing is if you want to check the Power inputs to the ECM using the multimeter.
Here's a link to them:
https://f01.justanswer.com/drhorsefield/5c6973f6-97dc-41d5-996f-eb2b3aceaaa5_TEST6.pdf
Page 4 shows the C2 ECM connector with the power input pins and the Class 2 data pin and you can backtrack the power wires through the previous diagrams to their power sources.
Power comes in on pins 1, 3, 17, and 36. The Class 2 Data Bus wire is at pin 48.
Here's a partial screenshot:
- I know how to get the key out. I just can't figure out why it keys getting stuck and the windows dont work at all. The pcm was replaced, all fuses are good, car runs fine. I don't know if the chip in key is bad , the BCM or something else . Im not sure what else I should look at as I'm not that familiar with these cars.
It had codes for multiple misfire, rich and lean condition, faulty cat, up and down stream o2 senors, multiple fuel injectors and a communication code. There were a few others but cannot remember what they are. The car ran like crap and had a extremely rough idle. After placing the pcm the car runs normal and has no issues at idle or anything. The codes are all gone and haven't come back. I don't have access to all data right now or any of my good scan tools. Something I did notice last month but forgot till now. When I hooked up my Apollo scan tool the blinkers came on and you can here a clicking noise coming from behind the cluster and behind the obd port. I'll start to back trace everything from the data bus and see if any of the modules connected to it are failing and causing the issues. Ill also double check the harness for the pcm. Right now it will have to wait till I can get my oscilloscope or fancy scan tool.
I got one of my good scan tools and ran OEM enhanced/ vehicle specific codes. It pulled a code for lost of communication with BCM. I didn't see that code as the cheap scan I used isn't able to run OEM codes. So I'm going to check the wiring and run a bench test to see if the BCM is truly bad and the cause of all the current issues but first I'm going double check the pcm and the can bus.