:: HOW TO...
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Brakes and wheels
Engine bay work
Some easy work
» Tuning: moderate
:: Tuning: moderate
:: Fitting a tuning chip on 20vt
1: Guidance for replacement of the EPROM in the EEC.
• 10mm socket and driver
• Torx screwdriver with large T9 bit
2: Removing the cover.
The EEC is located just above the passenger footwell. First, the plastic cover must
be removed. The two 10mm nuts (circled in red must be removed first, now the
can be removed.
3: Removing the EEC.
The controller is fastened with three 10mm nuts on a special metal carrier. These
must be carefully removed to prevent dropping them down behind the carpet.
With the nuts removed the EEC can be freed from it's carrier.
4 & 5: Undo the connector.
The plug is of a good design, which allows the connection without tools and gives
a good tight connection. The handle on top must be swung to the left. The cable is
loosened and can now be removed to the right.
6: Opening the EEC.
Unfortunately the housing is not only bolted, also held together with not very long
lasting bending latches. These must be bent first in the places cicled red in
the photo with some flat-nose pliers. Those not marked can be left. Then with the
torx screwdriver all the green circled screws must be removed.
7: Opening the EEC - Part 2.
The upper more solid part of the housing (baseplate) can now first be raised then removed.
Be careful not to bend the latches when raising the housing.
To avoid the danger of electrostatic shocks don't stroke your cat, walk across
carpets etc.. It is best to use a proper antistatic wrist strap and ground it.
8: The interior of the EEC (Information)
Voilà, the interior of the EEC. Down on the right the EPROM which can be
replaced (the "chip") is to be seen, still at the moment is the Bosch original.
It also applies here to touch the circuit as little as possible. The complex
circuits in the centre are performance semi-conductors (probable for ignition, injection
and other electrically operated components).
9: Development of the EPROM
For removing the EPROM, an IC-extractor is preferrable. This reduces the danger of
damage to thecircuit board or chip because the chip is strongly held in it's base.
In case an IC-extractor is not available, a pointed item eg a screwdriver, awl etc can be
The removed component should then be transferred to an anti-static bag as
soon as possible where it can be stored problem free for many years.
10: Begin the new building block.
The chip is first rested on the base with no pressure applied so it rests evenly on
all the connections. Then from above, press evenly with the thumb.
Importantly, support the board while pressing hte chip home to avoid damage from
the thrust forces.
Here, the chip replacement is completed. Finally, the whole disassembly procedure is
reversed to put the EEC back together.
For the test run, it is recommended that non all of the metal tags are re-bent
and the plastic cover is left off the EEC. When the EEC has been successfully tested
you can then go back and secure all the fasteners.