Greetings to all.

Newbie here. I recently bought a 2003 Z06...what an excellent driving machine!! It has the dreaded Column lock problem. Has the LMC5 bypass. I have read a couple of long blogs about the subject and decided to dig in to the BCM itself.
I am trying to identify the processor type with little luck. The numbers on all the chips appear similar and guessing that they must be GM part numbers. Attached is a picture of the circuit board in hopes someone could identify it. The processor is the large square chip on the board. If I counted right it’s a 68 pin chip.


BCM...Large chip on the top is what I need to identify.

Any ideas out there?

Thanks!!!

 

Not sure what that device is but some information on the web says that these were Motorola's or Intel CPU's. I am supprised that this information is not freely available.. Maybe GM could release it or the supplier of the BCM. If you did find out what the chip is, what would you do with that information?

 

Have you tried searching for the part or chip number on Digi-Key? They sell all sorts of stuff like this.

 

Thanks for the feedback Pdbrains!

Fortunately there are not many 68 pin PLCC microprocessors. Looking at several brands I found on line the pin outs of the power and cristal pins agree with the Motorola MC68HC11 and nothing like the other three I found. My original plan was to trace the assembly code and find the spot where the steering column is actuated and checked to make sure it is disengaged. I will either remove two relays on the circuit board and add timed circuits to exactly do what the program expects. OR find the end of the assembly routine that determines the health of the steering lock and change the result to always healthy. This is no small project!

Best Regards

 

Thanks For the feedback Trash!

Yes, I’ve spent a few hours searching. The number(s) on the chip gave no reasonable results. Digi-Key gave me the best information once I started looking for MCUs of 68 pins. Very handy for the search and links to data sheets!

Best Regards.

 

It's a pretty big job to reverse engineer the code without have the electrical schematics. Are you planning on dumping the contents of the eprom to get the assembly code? It's seems that the external signals from/to the BCM have already been figured out. There are schematics out there for building a circuit. Take a look at this link. http://shelor.net/Z/CorvetteForum/Cscokd/. It seems that you have the skills to redesign this to remove the relays and change it over to an all solid state design.

 

I had a LMC5 fail so don't discount that, I troubleshot the column lock down to either the relay or the LMC5. First replaced the relay then the LMC5 (a solid state switch) and that was the root cause.

 

Your link is familiar to me. This problem just seems to have several exterior factors (like low battery voltage mainly) that may trigger the problem. That’s why it just seems logical to remove the code that detects the condition. Assuming the MCU is a MC68HC11 it will have an EEPROM that would also need to be read in addition to the external EPROM. I suspect that when they talk about the BCM being flashed they are only talking about the EEPROM in the MCU. So both memories would need to be read to get all the code. I think it is interesting that despite two recalls that, I believe, involved reflashing the BCM, the problem was not eliminated. I wonder if the code that checks the lock is located in the EPROM and therefore was not modifiable unless the BCM were to be replaced $$$$ with a rewritten EPROM.
There are two relays in the BCM that control the column lock actuator. I read a comment from the LMC5 rep (probably designer) who suspects those relays to be a source of problems as the the car ages. So that is definetly a source of focus for me.
If the code is not touched then the key would be to find the exact timing expectation the MCU requires to qualify the steering lock as healthy. Once we have a time expectation the internal relays could be replaced with a precise trimming circuit.

 

Yes I did think of that possibility. As a troubleshooter I lean on fixing the problem at the root rather than workarounds that, although may save a ton of time and money, dońt completely eliminate the problem. Guess I’m a little obsessed about this problem.....lol.
I would love to go for a ride without my wife worrying about us getting stuck somewhere. 😕

 

Remove the lock plate/locking motor and ensure the PCM is programmed to not have the 2mph speed cutoff and you can't get stranded anywhere.

 

The lock motor is disconnected. Assuming you are talking about using something like the Tech 2 to flash modules; If the PCM is already programmed with the 2mph cutoff will the tech 2 allow you to go back to the previous state (Revision)?

thanks for the pointer.

 

So I don't know if they can go back to the previous state, I have read that they can just enter a very high mph number, like 200 maybe.

 

That sounds like a good idea. It should be easier to find that in the code. The only drawback would be getting the column message once in a while. The Reset button on the dash will clear it. I'll keep this option in mind.

Thanks!

 

Thought I would place un update here. After many hours of work I was able to add code to the BCM to simulate the steering column lock position expected response. Have had no problems for a month now!
Thanks for the feedback.

 

Very cool. Having heard of this problem many times over the last 3 years I've owned the car, I've always wondered if this circuitry could be replaced with a (not so) simple PLD. Hmm. I will look into it if mine ever fails.

 

I like that you were able to do this. Do you care to share how this was accomplished? What other interesting info did you find out about the hardware and software.

 

I'd love to know the details of this - how did you do it?

BTW, I'm one of the main developers of PCM Hammer so I'm no stranger to this field, I just haven't looked at other modules besides the PCM yet.

I'm itching to get the EBCM figured out next, and hopefully fix the "ice mode" problem, but any information about getting into any of the modules would be interesting.