GOT AN AFTERMARKET  ENGINE CONTROL EPROM?

E30 is a simple car to change the chip in, open the glove box, remove the 2 black Phillips screws from the black plastic cover above the glove box, do not open the gold anodized screws, they are for the catch.

At the rear, inboard side, of the panel is a 1/4 turn clip, there is another on the outer side also. Remove these, and remove the panel, leave the light connected as trying to disconnect it usually results in broken wires. The DME is the large silver box mounted under the dash top, remove the 10 mm bolts holding it in place, with the ignition off and key out of the ignition, unplug the harness by moving back the metal tab at the wire end of the connector, and lifting the connector out.

On later models, there is a metal lever folded over the plastic connector, pull this lever up and it will pull the connector out for you.

There were a few different types of DME, but most have some metal tabs bent over from one half to the other, these need to be bent back, don't worry if you break one or two. There may also be 2 or 4 screws in the top of the unit, remove these if they are present. Open the cover, from here on in, you should be suitably grounded to remove risk of damage from static electricity. Depending on model, you have one or two circuit boards inside. If you have one, you will see the EPROM under a plastic cover, remove the cover and gently remove the EPROM from its socket. Take note of the direction of the EPROM, one end has a notch cut in it, so does the socket, these must match. Do not rely on printing or stickers to align the EPROM, only the notch. Place the EPROM on the socket so all pins line up with holes and gently push it in with your thumb.

If you have two circuit boards, the EPROM is located between the two, and they must be separated. In the centre of the assembly is a white pin, it protrudes through the bottom of the case, remove the centre of the pin, from the outside of the case. Next gently pry apart the plastic legs separating the corners of the board and the pin connecting the centre of the board. Some units will have a screw holding the top board to the assembly, for grounding purposes, you must remove this now. Now look at the connector, at either end of the pins for the top board, there is a plastic tab, gently pry the tabs inwards, while raising the back of the top board, this will allow you to get the top board to an angle of around 45 degrees. Now you need to pull the board out of the connector. Look closely, the boards connector will catch on the fixed connector, you must use a screwdriver to pry one past the other. Pull one corner out first , rather than pulling the entire board evenly.

Then locate the EPROM and continue as described for the single board units.

Above all, be gentle , take your time, and don't use excessive force, one slip could cost you some serious dollars.