Remove/Replace DME Chip
by: Jon Kaminsky (jon@rennlist.com)
Date: August 10, 2002
you know your way around these regions, you can do it with the seat in place. You need a metric allen wrench to get the seat out and it's not easy working the wrench in there. It is also recommended to disconnect the battery from the electrical system to minimize any chance of damaging sensitive electrical components. However, the author admits that he rarely follows this advice.
To round-trip the chip, follow these steps:
1. Assuming you are not going to remove the seat, move the seat all the
way back and all the up on the height adjustment.
2. Remove the carpet mat(s). One of the mats will have a hard plastic
piece convering the electronic control unit (ECU).
3. Near the front of the seat on the ECU, there is a black lever with a silver hinge.
It's difficult to explain how it works, but in essence you draw the lever
back to release the harness from the silver colored metal ECU unit.
4. With a 10 mm wrench, unfasten the nuts holding down the ECU unit under
the seat. There are four nuts on long bolts which make it a bit difficult.
You might be able to use a 10mm socket if the socket is tall enough to go
down over the long bolts and get a purchase on the nuts.
5. Pull the ECU unit out.
Now the semi-difficult part begins....
6. There are perhaps 8-10 tabs on the ECU housing (cover) you will have to pry up to
remove the cover.. A small bladed screwdriver and
needle-nose pliers work pretty well. Once that is done, you should be
looking at a PC board with a floppy plastic shield, all mounted to the
base of the can on whitish plastic stand-offs. Be sure to discharge any
static electricity you may have picked up by touching a grounded metal
object before touching the PC board.
7. You will have to separate the stand-offs by gently prying apart. It's a
pin-socket arrangement and you have to apply some pressure to get the
plastic pins out of the sockets. You can try inserting a small flat-tip
screw driver in the slit on each post and twist slightly while pulling
gently at each post. I've also used pliers with plastic padding
taped over the metal jaws and opened the pliers between the halves of the
two parts to ease the pins out of the sockets. Be careful you don't damage anything when the pins suddenly let go out
of the sockets. Once the pins are separated from the sockets you will have
two halves attached by a floppy cable. Now the very hard part....
8. Look to the FRONT of the half with the PC board, you will see the
connector portion that was connected to the harness lever in step 3. This
has to be pushed out of the surrounding housing. To do so, on either side
of the metal connectors there are small tabs. You need to use small
screwdrivers to push the tabs down while AT THE SAME TIME, push the
connector portion backwards out of the housing (toward the back of the PC
board. If you didn't remove the pins in step 7, this will not budge. If
you look hard enough, you will detect a seam all the way around the
connector portion and sometimes a third small screwdriver worked in to the
seam between the top of the connector and the housing helps ease it out.
Figure 1 shows what the connector portion looks like.
Figure 1. Connector portion of the ECU.
9. Once this thing has been pushed out of the housing, you can get access to the chip. There may be a little milky white "H-shaped" cover over it. It's a small EPROM, in most cases, manufactured by Intel Corporation, and it looks just like the one you are replacing it with. There should be a small silver colored sticker on top of the chip. If the chip is not stock, it may have a sticker on it identifying the after-market programmer. Do not remove these stickers- the sticker protects the crystal window which if illuminated by UV light, can erase the chip. Again, be sure to discharge any static electricity you may have picked up by touching a grounded metal object before touching the EPROM chip. The corner of the chip should be marked with a bevel or a dot to indicate orientation- NOTE THIS ORIENTATION. The chip needs to be very carefully pried up out of its base. It's best to use a small screwdriver to gently pry underneath the chip, alternating from end to end until the chip is out. Do NOT pry up or otherwise damage the socket the chip fits in or you will be VERY unhappy with the results.
10. Be sure to discharge any static electricity you may have picked up by
touching a grounded metal object before handling the new chip. Insert the
new chip, orienting by the marked corner, by gently aligning the new chip
with the socket holes and pressing in.
11. Reverse the disassembly steps and you're done.
It's all quite easy except for step 8. Just be patient. First time it
should take about half and hour. With practice, you can do it in half that.