Installation instruction
Chip in BMW Motronic
For model E31 / E32 with M70 Motor
(12 Zyl.)
PLEASE READ THIS INSTRUCTION
TO THE VERY END
BEFORE STARTING THE JOB !
This is an installation
instruction describing the exchange of the original chip with a reprogrammed
high performance chip.
The pictures
are partially taken from a BMW E34 / 540i, but can also be referred to for
other BMW model’s ECUs.
Necessary tools
Size 2 Philips
head screwdriver, needle nose pliers, ratchet with 10mm nut (see text),
screwdriver about 5mm wide, screwdriver about 3mm and eventually a torx
screwdriver (see text), normal pliers.
Location of the ECU
In the E32 the
ECUs (the M70 engine has two ECUs, one per cylinder bank) are located under a
large black plastic cover right in front of the bulkhead. This cover is secured
with 4 large Philips head screws.
What are the functions of the various ECUs?
Under the
plastic cap you find three units at the 850i/ci while you see four at the
750i/iL.
(the picture
shows a E32-V8,but it looks identical on the V12 cars)
.
850i/ci from windshield:
EML
- DME1 – DME2. DME (Digital Motor Electronic) is a more specific
expression for ECU (Electronic Control unit). The transmission ECU is located
in the trunk.
750i / iL from windshield
DME1 – EML – DME2 – transmission ECU
EML is the electronic throttle control unit.
How to take out the DME and where to find the Motronic
(DME) number?
All ECUs are either secured with M6 nuts (earlier
models) or secured with special clamps (later models).
Prior
to unmounting the units detach the big black connectors and carefully bend them
aside.
On
the DME one can find several stickers. Only the large one is of any relevance
carrying the number 0 261 200 xxx
XXX
stands for either 156 (ONLY E32 up to 1992 with M70B50 engine) or 352 (ALL E31
with M70B50).
Opening
the DME
After having taken out the DME the
unit needs to be taken apart in order to change the socketed chip.
First of all
the cover carrying the number sticker needs to be taken off. On later units the
aluminium cover is secured with additional torx screws which need to be taken
out first.
Afterwards loosen the clamps on the
back side of the unit. This is easiest with the 5mm wide screwdriver. It’s a total
of 6 clamps which like to break off on the aluminium covers which isn’t a big
dilemma though. The torx screws are strong enough to hold the cover.
Now the cover can be taken off and the
one of the main differences between the 156 and the 352 ECUs becomes obvious:
The 156 ECU has two PCBs (printed
circuit board) while the later 352 has only one.
The next steps
describe how to take apart a 156 ECU. If you have a 352 unit you can jump to
the section describing the removal of the chip.
Detaching the two PCBs from each other
(DME 156)
The chip is located on the upper PCS
hidden under an either black or white plastic cap. In order to get access to
the chip you need to detach the two PCBs from each other which is a bit tricky.
For this exercise you need both screwdrivers (3mm and 5mm) as well as the torx
driver.
The PCBs are attached to each other at
five points:
Via a torx screw, two plastic
connectors in the back of the unit and in the front where the electric
connections are. This is the tricky part because here the connection is over
the full width of the unit plus additional clamping on each side. The fifth
point is in the middle of the unit (white spot in the above picture).
First
step is to unscrew the torx screw securing the PCB to the unit’s case. Next
open the little white plastic connector in the middle of the PCB (see picture)
connecting the two PCBs.
:
After
this open the rear two plastic connectors by pulling them apart:
Now
on the front side open the left and right plastic clamp:
Just
bend them open with the 5mm screwdriver. Normally they stay in this position
afterwards:
Now
the horizontal clamping needs to be opened, which is tricky but possible…
…if
you push the upper PCB backwards at the same time. In some cases the upper PCB
is very stubbern and if so it helps to warm the connector side with a hair
dryer or a heat gun set to low temperature. Once you have achieved this it
looks like on the below picture:
Now
you can flip it open which looks like below:
After removing the plastic cap (the
white one in the above picture, can be black as well) it looks like below:
Carefully
remove the chip from the socket by using the 3mm screwdriver. Please note that
the chip has a little marking (slot) on one of the short sides pointing to
where the finger is on the above picture.
When installing the new chip make 100% sure the mark shows in the same
direction.
Mounting the chip the wrong way around can
kill it !!!
The Top speed limitation (Vmax)
is NOT programmed into the DME chips but in the EML chip. In order to get rid
of this limitation the EML chip needs to be replaced as well. The mechanical
construction of the EML ECU is similar to the 156 DME. The necessary steps to
open the EML ECU are according to the ones described before for the 156 DME.
DISCLAIMER
This installation instruction has been
written according to the author’s own experience and does not claim to be
correct and / or complete. It is just meant to be supportive and if you are not
completely sure to be able to do the job please see a specialist.
The sole
responsibility for the correct installation of the performance chips is with
the person performing the installation.