Removing and installing engine control unit 2 J624: Audi 4.2 (BNS, BUJ, BYH, CMPA, …)

Removing and installing
engine control unit 2
J624
Special tools and workshop equipment required
Hot air blower (220 V/ 50 Hz)
VAS 1978/14
item 1
with nozzle attachment
2
from
wiring harness repair set
VAS 1978
Small, commercially available mole grips
3
Note
The engine control unit
1
is bolted to the protective housing
5
. To make it more difficult to unscrew the shear bolts
4
for locking plate
2
, their threads have been coated with locking fluid.
The protective housing has to be removed before the connectors can be unplugged from the engine control unit (e.g. to connect the test box or renew the engine control unit).
Removing
When renewing engine control unit, select diagnosis object
“Replace engine control unit”
in
“Guided Functions”
mode
vehicle diagnostic tester
.
Switch off ignition and remove ignition key.
Fit protective covers on bodywork
Chapter
.
R8 Coupé:
Remove engine compartment trim panel (left-side)
Rep. gr.
53
.
Unscrew the nuts from the four retaining clips for
engine control unit 2
J624
and swivel the retaining clips to the side.
Remove
engine control unit 2
J624
3
.
R8 Spyder:
Detach cover
1
.
Unscrew bolts
arrows
and remove together with retaining clips.
Remove
engine control unit 2
J624
.
All vehicles:
To help prevent unauthorised access to the connectors on the engine control unit, the control unit is secured by means of shear bolts to a locking plate and a protective casing.
The threads of the two shear bolts
4
which are not screwed into the engine control unit are secured with locking fluid. To unscrew these two bolts, the threads must therefore be heated with the hot air blower.
The threads of the two shear bolts
3
which are screwed into the engine control unit are not secured with locking fluid. Do not apply heat to the threads in the control unit housing; this is not necessary and would cause overheating of the control unit.
Select settings on hot air blower as shown in illustration, i.e. set temperature potentiometer
2
to maximum heat output and two-stage air flow switch
3
to position 3.
WARNING
Heating the thread of the locking plate also heats up the shear bolts and parts of the metal housing. Take care to avoid burns. It is also important to ensure that only the thread is heated and none of the surrounding components if at all possible. These should be covered if necessary.
Apply heat to the threads of the shear bolts on the connector side as shown in the illustration.
Switch on the hot air blower and heat the bolt for approximately 20 ... 30 seconds.
Unscrew shear bolts using suitable vice-grip pliers (see arrow in illustration).
The two shear bolts screwed into the engine control unit do not need to be heated. They should be removed without being heated.
Detach metal locking plate from connectors.
Unscrew two bolts securing retainers for
engine control unit 2
J624
.
Release connectors on
engine control unit 2
J624
and unplug connectors.
Take out old
engine control unit 2
J624
and install new
engine control unit 2
J624
.
Installing
Installation is carried out in the reverse order; note the following:
After installation, the locking plate must be re-fitted on the
engine control unit 2
J624
.
Clean threaded holes for shear bolts to remove any residue from locking fluid. This can be done using a thread tap.
Always use new shear bolts.
After installing a new engine control unit, the following operation must be performed:
Activate engine control unit via a vehicle diagnostic tester in
“Guided Functions”
mode,
“Replace engine control unit”
.