1994-95 BMW 530i/540i Chip Install Instructions

These new instructions should help owners of the 530i/540i install any aftermarket Performance Chip into a Bosch ECU ending in "404" or "484". Almost all of the pictures below are clickable for a super-sized image.

Take the ECU to your workbench after you have removed the ECU from your car. Remember to discharge any static electricity that has built up on your body. For tools, you will need a small flathead screwdriver, a medium flathead screwdriver, blunt-nose pliers, and a T20 Torx wrench (we include this last tool).

Verify that the ECU number is 0 261 200 404 or 0 261 203 484. On a TMS Performance Chip, the last 3 digits in the ECU number should match the FIRST three digits on the Performance Chip. On the "404" ECU there should also be a "1744050" number present on a separate label. If this number - pictured below next to a green arrow - is not on your ECU, call Turner Motorsport for instructions on getting the correct chip.

•   Unscrew the four Torx bolts on top of the ECU.
  
•   Flip the ECU over so the part numbers are facing down. Take one of the flathead screwdrivers and gently pry the locking tabs holding the ECU cover to its base. These tabs are very weak and will most likely break off while you are doing this.
  
•   Once all of the tabs are bent back, flip the ECU over and pull the cover from the ECU. You should see something like this:
  
  
  
• Notice that there are two printed circuit boards. On one end is the port where the car's wiring harness plugged into. The uppermost row of pins is connected right to the upper circuit board. On the other side is a ribbon connecting one board to the other. By following the steps below you will be separating the upper board and folding it over to sit next to the lower board. YOU WILL NOT BE DISCONNECTING ONE BOARD FROM THE OTHER or cutting the ribbon or any other magic trick. Have patience and study the ECU carefully and you will successfully install your Performance Chip.
  
• Next, insert the small flathead screwdriver into the cone-shaped post sticking up in the middle of the upper board (see photo above). You will see slots to insert the screwdriver into. Inside this cone is a rod that locks the two circuit boards together. With the small flathead screwdriver, push this rod down. It will come out on the bottom of the ECU. Use the pliers to pull further but you do not need to pull the rod completely out.
  
• There is a T20 Torx bolt holding the upper circuit board to the ECU. When looking at the ribbon from behind this Torx screw is on top on the left.
  
  
  
• Hold the ECU in your hands with the wire harness plug facing away from you and the circuit board facing up. Position your hands so that you can push the upper circuit board with your thumbs. See the photos below. The snap connectors on either side of the ribbon will need to come undone. To do this press firmly on the upper board with your thumbs while holding the ECU stable. You can do one at a time. MAKE SURE THE TORX SCREW IS REMOVED FROM THE UPPER BOARD.
  
  
  
• The final lock holding the upper board in place is on the wire harness plug end. They are very hard to see. There is a tab on each upper corner of the plug housing. Look past the very last pin in the upper row and you should be able to see them. Insert the small flathead screwdriver and pry these tabs toward the inside of the plug housing. Get these good and loose but do not bend them too much (they will break). See photo below.
  
  
  
• Now, turn the ECU around so that the plug housing is facing away from you. Push up on the upper board with your thumbs again until the ribbon is almost fully extended. There will be a lot of resistance to doing this - both from the ECU and your own sensibilities - but you have to push the upper board far up.
  
  
  
•   The upper board is actually attached to the uppermost row of pins in the wire harness plug. Hold the ECU in your hands, and with the ribbon fully extended, gently pry the upper board AWAY FROM the wire harness plug housing. The goal here is to push the uppermost row of pins out of the plug housing. Remember that this ECU has probably been assembled in this way for ten years. It will give you some resistance. If all seems lost, try pushing up on the ribbon some more. The angle of the upper board is crucial to pulling it away from the plug housing.
  
  
  
  
• When the upper board comes free, the ECU should look like this:
  
  
  
• Note the position of the divot on the stock chip. The Performance Chip must be oriented in the same direction. The TMS Performance Chip uses an arrow to denote the divot end. The stock chip is located in a socket (in the red circle in the picture above). Insert the small flathead screwdriver into one end of the chip and pry upward. Alternate ends to remove the chip without bending any of the pins. PRY THE CHIP FROM THE SOCKET - NOT THE SOCKET FROM THE CIRCUIT BOARD!
  
• Push the Performance Chip into the socket. Remember that it must be in the same orientation as the original. Make sure that all of the pins are seated and all of the socket's holes have a pin in them.
  
• Fold the circuit board over into the ECU and insert the row of pins into the housing. Pay particular attention to the cone-shaped post in the middle of the ECU that must go into the hole on the upper board. When all is lined up and clear push the circuit board into place. Push down so that the snap connectors re-connect. Re-install the Torx screw into the upper board. Push the retaining post back up into the ECU. Slide the cover on and reinstall the four Torx screws and bend the tabs back into place. If they are broken off and the cover is loose, you can use tape to seal the edges of the cover.
  
• Reinstall the ECU into the car and enjoy!