I have a 98 M3 convertible that the door for the top intermittently won't open. I have a laptop with a GT1 on it and can't access several control units including the top control unit. The top works fine sometimes and other times it gets to the point where the storage cover should open and nothing happens. Some times I drive a few feet and it works again. Looking to see if anybody else has had this issue and what they found. I have only had the car a few months. I have unplugged all of the control units that are on the bus except for the top unit. I unplugged the ABS, GM, Cluster, Heater, OBC and still can't communicate with any of those control units. I have found I can communicate with the DME at the plug under the hood but not the OBD plug in the car. Seems to me there was an old BMW bulletin about reflashing the DME for that issue. Just looking for some ideas. Thanks.
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You need a true ADS interface to access all modules. GT1 is the whole system/diagnostic head, you have that? Or the DIS/Inpa software?
There is a trunk/stowage lid interlock. Could prevent it from opening.
And if it's when opening the top, there is a microswitch in the frame that tells the module the rear window bow is up, now open the cover.
When it happens, pull the rear bow up and towards the front. Maybe the switch doesn't get actuated correctly. Or it's failing. -
Today I unplugged the DME and Trans control units to see if I could contact the other control units. No help. I just pulled the L/R Door panel speaker cover and tomorrow I will unplug the top control unit and see if I can communicate with any of the other control units. Pretty hard to diagnose the top when you can't connect to the control unit. I can connect to these control units on my other cars.Comment
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Yes it is an intermittent thing but happens quite often. After studying the way over-complicated system for weeks I keep thinking I know the answer. Then I find out I am still in the learning process. Thanks for the tip about the ADS cable. I am in the process of ordering a cable that will communicate with the control unit so I can monitor the switches. My latest theory is the tension bow does not always go all the way up to trip I believe S1 switch. Then I close the top and try again and it goes all the way up. I can see the bow is not all the way up but don't see why its not. I think I may have it figured out by the time the snow falls. Right now its in the garage with the top down. I'll keep posting my progress and hope others will chime in. Thanks.Comment
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People often have problems about the tension bow not going fully vertical. But the stowage lid always opens. Hence why so many have problems of it hitting the top.
So fully vertical is not a requisite for the lid to open.Comment
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