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Exhaust emissions warning lamp K83 in dash panel insert > < Replacement procedure for engine control unit without protective housing

A3 Mk1

Procedure for replacement of engine control units bolted to a protective housing (locking element)
Procedure for replacement of engine control units bolted to a protective housing (locking element)
Removing
–  Connect up the vehicle diagnostic and service information system -VAS 5052- and select vehicle system “01 - Engine electronics”. The ignition must be switched on when doing so.
   
The vehicle diagnostic and service information system -VAS 5052- displays the control unit identification and the code -2-.
–  Always start by displaying and printing out the control unit identification.
–  Switch off ignition.
–  Unscrew the wiper arms.
–  Detach the plenum chamber cover and set it down towards the windscreen.
  Note
Item -1- in the illustration shows the engine control unit with protective housing.
  A24-0540
To make the connectors at the engine control unit less accessible, the engine control unit -1- is bolted to a protective housing -4- by means of a locking element -2- and shear bolts -3-.
To make it even more difficult to screw out the shear bolts, the threads are coated with locking fluid.
The locking element -2- must be separated from the protective housing to enable the connectors to be unplugged from the engine control unit (e.g. when connecting the test box or replacing the engine control unit). This procedure is described in the following.
Special tools and workshop equipment required
  A24-0540
t  Hot air blower -1- (from wiring harness repair set -VAS 1978A-)
t  Commercially available vice-grip pliers
Procedure:
  WARNING
Exact compliance with the following operations is essential so as not to damage (scorch) wiring, connectors, insulation and control units. Heed the operating instructions for the hot air blower.
  A24-0475
So as to avoid damaging wires and connectors, fit plates to provide a screen (items -1- and -2-). This is designed to stop the connector housing and wiring harness becoming hot.
  A24-0538
–  Select the settings on the hot air blower as shown in the illustration, i.e. set the temperature potentiometer -2- to maximum heat output and the two-stage air flow switch -3- to position 3.
  Note
Then heat the bolt of the locking element with the hot air blower. This step reduces the inhibiting action of the locking fluid on the shear bolt threads, making these easier to unscrew.
  WARNING
The shear bolts and parts of the metal housing also become very hot when heating the thread of the locking element. 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.
  A24-0476
–  Move the nozzle -1- of the hot air blower towards the bolt -2- of the locking element.
  Note
Particular care is to be taken in this case as the control unit connectors are in the immediate vicinity.
–  Switch on the hot air blower and heat the thread for about 20 to 25 seconds.
  A24-0537
–  Then grasp the head of the bolt -2- with the vice-grip pliers -1- and unscrew the shear bolt in arrow direction.
–  For greater protection, the locking element is mounted such that it is not possible to give the vice-grip pliers a full turn.
The procedure for the second shear bolt is exactly the same. Particular care is to be taken in this case as the control unit connectors are in the immediate vicinity.
–  Once the second bolt has been taken out, the windscreen wiper system must be removed. → Electrical system; Rep. Gr. 92; Windscreen wiper system; Removing and installing windscreen wiper system
  WARNING
The control unit is not to be pulled over the locking element -6- as this could strain and damage the control unit.
–  Then pull out the engine control unit with the retainer.
Following removal, the locking element is to be unscrewed from the retainer. The control unit is not to be pulled out until the locking element has been removed.
  A24-0539
To make it more difficult to pull out the engine control unit -1-, the locking element -2- is bolted onto the protective housing with the shear bolts -3-.
To make it even more difficult to screw out the shear bolts, the threads are coated with locking fluid.
–  Clamp the control unit in a vice
Installing
Installation is performed accordingly in the reverse sequence.
–  The protective housing must always be re-attached to the engine control unit.
–  Remove remnants of locking fluid from the tapped holes for the shear bolts. This can be done by using a thread tap.
–  Always use new shear bolts.
–  Bend back the retainer tab of the mount.
The following operations must be performed after connecting the new engine control unit:
–  Code engine control unit → Chapter.
–  Perform adaption of throttle valve module -J338- → Chapter.
–  Perform adaption of kick-down function for vehicles with automatic gearbox → Chapter.
–  The immobilizer must be enabled using vehicle diagnostic and service information system -VAS 5052-.
–  In “Guided Fault Finding” mode, “Select type” menu, select the option “Remaining vehicles for online immobiliser interface” and follow the instructions in Guided Fault Finding.
  A24-0543

Exhaust emissions warning lamp K83 in dash panel insert > < Replacement procedure for engine control unit without protective housing