ZKE/GM5 won't code; windows and convertible functionality
Hey everyone, I have an interesting one here. This E46 convertible came in because the top wouldn't function, and the rear 1/4 windows wouldn't roll up. I checked fault codes and found there were faults for all four windows' anti-trapping. Take note that the front windows roll up and down with the switches, but won't "auto-up or auto-down". I also learned that I can activate the rear windows to go UP with the scan tool only. Each rear window will go down with their respective switch, and the LR window goes down when you press the 'all windows down' window button, but the rear windows won't roll up with the switch, let alone learn their auto-up function. Lastly when you open either door, that window will roll down slightly, but will NOT roll back up when the door is closed.
Ok so looking at scan data, I can see that all the window switch inputs read correctly in the GM (ZKE) control unit. Looking in the CVM (convertible) module, I can see that all the latch inputs: top latches, stowage cover, etc is all closed/latched. So there should not be a reason that the CVM would be preventing the GM from using the rear windows.
The second problem is the convertible top will function up until the point that the stowage compartment lid is supposed to open. It stops because the GM is supposed to provide the ground for the stowage lid latch actuator control relay. If I provide the ground myself, then the convertible top will continue to function, *with some assistance. I found that there is a hydraulic leak in the system. Fluid was low and I topped off. It also needs the assist-struts. The convertible top, however, no longer seems to be a priority for the customer. Customer only wants the windows to function at this time.
I tried to code the original GM and it failed. I coded all the control units then, including the GM, and all passed EXCEPT for the GM. I did this with my Autel Maxisys AND my ICOM w/ ISTA/P subscription. I get the verbatim fault: "Global.VehicleCommunnication.CoAPI.1000 - (CoAPI) - General Fault". I now also have fault code 44: GM5 not coded.
I optioned the customer on a new or used GM. Customer went for used (I don't know if this is a problem or not). Replaced the control unit, coded it with ISTA/P, and I have all the exact same symptoms. The only difference now is the rear windows will not go up, even when the scan tool activates them. The used GM coding fails the same as the "original" GM did. If I put the original back in, the scanner will roll up the rear windows.
One final detail I need to mention is that the original GM had a lot of dielectric grease in the two connectors with smaller pins. Connectors are clean, but that tells me someone has been in there before. I wonder if this GM was replaced with a used one and was not coded properly during the repair (or would not code if attempted). I talked with the customer further, and learned that he has had the car for 5 years. Top and windows all operating normally until last year. He tried to use the top last summer, and this all started. Car was not sent to another shop. He parked it in his garage until this summer.
I do have a few questions:
1. Can you put a used GM in a car and code it, or is that not something that normally works?
2. Is there something else I missed diagnostically that I need to look at before condemning the GM?
3. Will these symptoms be present due to a coding error of the control unit, or is there something else going on here (or do I have two faulty units?)?
The windows do operate smoothly. I checked all of the fuses: 12v run through all of them, and there are no fuses missing. I personally think that I have two failed control units, but want to make sure I am covering all of my bases here. Let me know if there is anything I missed or need to look at.
Thanks for the help!
Check the position switches for the top. there use to be a broken wire in the top above the drivers head so it never saw the top latch to the windshield frame. If I remember right the glass behave poorly if it does not see that switch closed.
Well the scanner will read correctly when the front latches are locked or unlocked. If it reads locked, I don't think that is what would inhibit the windows from functioning.
You can definitely go with a used GM5. Those were routine failures back in the day. Another common symptom was failure of the central locking relay which is incorporated into the GM5. Lots of folks try to repair them, due to cold solder joints. Open that one up, and do not be surprised if it has already been tampered with. Finally, do not shy away from a brand new unit. They are not that…