Removing and installing engine control unit J623 (with metal locking plate) — VW

Removing and installing
engine control unit
J623
(with metal locking plate)
Special tools and workshop equipment required
Hot air blower
VAS 1978/14A
item 1
with nozzle
2
from
wiring harness repair set
VAS 1978 B
Small grinder (commercially available)
Vehicle diagnostic tester
Removing
If the
engine control unit
J623
is renewed, the adaption values must be read out and stored before the
engine control unit
J623
is removed.
The procedure is described in
“Guided functions”
mode, test sequence/function
“Replace engine control unit”
. Use
Vehicle diagnostic tester
for this.
Save adaption values in a file.
After you have saved the adaption value file, switch off ignition, and pull out ignition key.
Note
If the adaption values of the injectors cannot be read from the old (defective) engine control unit anymore, the adaption values must be entered manually into the new engine control unit.
Caution
If the engine control unit comes into contact with the positive battery terminal, the engine control unit will be destroyed. For this reason, the battery always needs to be disconnected prior to removing the engine control unit from its bracket
Electrical system
Rep. gr.
27
Battery; Disconnecting and connecting battery
.
Release retaining clip
arrow
and take out
engine control unit
J623
.
Make groove (for a screwdriver) in head of shear bolt
1
using a small grinder
2
.
Note
The threads of the shear bolts are secured with locking fluid. To unscrew these bolts, the threads must therefore be heated with the hot air blower.
Set hot air blower as shown in illustration. Meaning potentiometer for temperature regulation
2
set to maximum heating power and 2-stage switch for air volume
3
set to position 3.
WARNING
Risk of burns from hot air blower.
When heating up the thread of the locking mechanism, the shear-head bolts and parts of the sheet-metal housing become hot as well. Ensure to only heat up the thread and no surrounding components. Cover surrounding components, if necessary.
Hold
hot air blower
VAS 1978/14A
with nozzle attachment
arrow
to thread of shear bolt.
Heat shear bolts for approx. 20 to 30 seconds.
Unscrew shear bolt
1
using screwdriver
2
.
Detach metal locking plate from connectors for
engine control unit
J623
.
Release and unplug connectors.
Installing
Installation is carried out in the reverse order; note the following:
The metal locking plate must always be re-fitted on the
engine control unit
J623
.
Clean the threaded holes for the shear-head bolts of locking compound residues. This can be done by using a thread tap.
Always use new shear bolts.
After a new engine control unit has been installed, the following work procedure must be carried out:
Activate engine control unit with the function
Replace engine control unit
on
Vehicle diagnostic tester
in
Guided functions
mode.