This document is about installing a performance chip on a 1993 – 1995 BMW 325i or 525i ecu.
First of all, let’s locate the ecu so we can unmount it from the car. It is locate under the hood, in the engine compartment.
Refer to the drawing above; facing rearward, towards the windshield, at the upper left hand (passenger side), you will see a soft foam cover. Remove the (3) black plastic buttons that are on top and pry out the plastic tab centers to remove them and then remove the insulated foam cover.
Now, you will see a hard plastic cover. Remove this cover by removing the (4) top screws.
You will see the ECU box attached to a wire harness. Remove it by pulling it out. The ECU will just slide out.
Do not disconnect harness until the ECU is completely removed. For disconnecting the harness, just pull out the lock lever, in the direction showed by the red arrow in the picture at the Right.
If your BMW is the E34 chassis model, the ECU is located under a plastic cover, as showed by the red arrow in the picture above.
Please, DO NOT remove any bolt from the ecu.
There are (6) tabs holding the cover at the bottom. Using a small and sharp flat screwdriver, CAREFULLY bend the tabs away, so you can take the cover out from its original place. Please take EXTRA precautions when doing this and also when reinstalling the cover, to (1) avoid cutting your hands / fingers if the screwdriver slips and (2) avoid breaking the tabs, as they have proven to be very, very fragile.
Now, inside of the ECU, there is a white plastic cover on top of a chip. It looks like an “H” (picture below). The chip bellow it is the one to be replaced, so please unsnap the plastic cover and BEFORE removing the chip, please note the alignment of its pin #1, so the new chip can be inserted the same way (see a note about this at the end of this document).
Take out the chip by using the same small flat screwdriver and slide it CAREFULLY under the chip for slowly pulling / prying it off its original place, little by little, from both sides. If you have a simple chip pulling tool, you may use it instead.
Install the performance chip, by inserting it in the socket. For doing this, point pin #1 to the same corner as the old chip, then, carefully aligning all the pins into the holes and pushing it down firmly, securing it on place. Re insert (snap) the plastic “H” shaped cover. Now you are ready to put back the ecu cover, reinstall the ecu and enjoy your NEW CAR!!!
A word of caution about installing chips
Website's recent related searches: