I want to replace the EPROMS in my MOTRONIC 2.7 cpu ('91 348 TS) have opened the box by bending the small alu lip fasteners all around, but found that the EPROMS are sandwiched between two printed boards. What seems to be the best way to get to them? Has anyone done this before? Anything to watch out for? Thanks very much for your insights!
I haven't specifically replaced EPROMs on a 348 Motronic control unit, but I would bet that they are the same as other Bosch 2-board control units. I would highly recommend the use of an anti-static strap to ground yourself and the control unit, in order to prevent static electricity from damaging any of the electronics. They should be available at your local Radio Shack. In order to replace the eprom, you will have to separate the upper board from the lower board/housing. It sounds like you have already removed the outer cover. On the bottom of the housing in the middle you will find a small white plastic pin, carefully pull it out all the way. If you follow where the pin went, you can see that it spreads a clip/tube that is inserted through the middle of the upper board, this will have to be compressed in order to release the middle of the board. At the end of the boards opposite the large female connector that the main harness plugs into, you will see a ribbon wire that connects the two boards. on either side of the ribbon wire is a male/female plastic connector that joins the two boards. Carefully separate these two connectors ( I use a pair of snap ring pliers with flat ends), at the same time there are two clips that have to be released inside the female main electrical connector. If you look directly at the pins of the connector on the upper board, at the outer edge you can make out a flat black plastic pin on each side. These have to be released towards the center of the connector in order to be able to tilt the back end of the circuit board upwards. Now raise the back end of the board upwards until the ribbon cable limits its travel, then unhook and remove the front end of the board from the main female connector and lay the upper board out next to the lower board. There may be a cover securing the EPROM, insert a small screwdiver into the small slots to release it. Get a EPROM removal/install kit at Radio Shack. Pull the old EPROM out using the removal tool, noting the position of the notch on the end of the EPROM. Carefully install the new EPROM with the notch in the same orientation. Make sure that all the EPROM pins line up with the socket before pushing it in. The assembly is the reverse of the above procedure. Be very carefull not to flex or strain anything. It is hard to explain, but once you have figured out how to release the upper board, it will come out easily. If you need more detailed instructions with images, try contacting Dinan Engineering (the BMW performance shop in California) and see if they can fax you their chip installation instructions. Good luck, Brian
