ECU EPROM socket modification instructions

Motronic M1.5 ECU removed from the car ready for investigation.

An "un-touched" Bosch 0 261 200 356 automotive ECU for Vauxhall Senator 24V and Carlton GSi 24V models. The later versions were not fitted with a socket to hold the firmware EPROM. I guess Bosch thought they had perfected their firmware :-) or were cost cutting! There is no way to tell from the outside of the ECU so you need to get into it!

Securing tabs bent ready for lid removal.

The tabs securing the lid need to be bent back using a pair to pliers or a screwdriver. The lid can now be removed.

Once inside you can see if you need to fit a socket. The 'chip' is a 28pin EPROM which a white/silver ID label shown in the top left of the photograph below. If this is already in a socket it is just a simple matter of removing it and fitting the replacement. If not, then it's time to find some tools!

The lid off.

Tools required to fit a socket.

Soldering iron, solder sucker, good electronics wire cutters, solder are required. A couple of Torx™ screwdrivers are also needed to remove the bolts holding the PCB to the metal base of the case. Plastic P.C.B. mounts are also used, the three white blobs in the photograph above. The middle of these mounts needs to be pushed out before the board can be removed.

A standard EPROM removed by snipping the legs.

If the original EPROM is now longer needed the easiest way to remove it is by snipping around the pins from the top, as shown above. This leaves the pins still soldered into the P.C.B. Use the solder sucker and remove solder from each hole. Use the soldering iron on each individual pin until it is loose then pull it out (make sure the solder is molten before pulling as it is easy to pull one of the plated through hole out with it!). A couple of the pins are quite difficult as they are part of a large ground plane which conducts heat very well, these pins can be seen below when backlit (pins 14 and 28). After all the pins are out go around the holes with the solder sucker and clear all the solder from them.

A ray of light! 28 clean plated holes ready for a socket.

This is what you should end up with. 28 nice clean holes ready to accept the socket of your choice! The one shown below is a expensive Aries variant, handy if you change chips regularly, otherwise a good quality turn pin gold plated version is more than adequate.

A new  Aries locking socket in place. 

Make sure the new chip (and the socket if it has a orientation notch) is fitted the correct way around. Look the picture of the standard EPROM above, the locating notch on the chip should face toward the edge of the board. I don't know about you but I was always taught, when laying out PCBs, orientate all the IC's in the same direction, check out the IC below the socket...naughty Bosch!

Job done! Bolt the PCB back onto the base and refit the lid by bending back the tabs.