audi Workshop Repair Guides

Audi Workshop Service and Repair Manuals

ABOUT US
Procedure following interruption of power supply > < Wiring and component check using test box V.A.G 1598/39

A4 Mk2

Motronic Direct Injection and Ignition System (4-Cyl.)
Servicing injection system
Replacing engine control unit

Note:

Unplugging connectors from engine control unit erases learned values, however content of fault memory is retained.

Removing engine control unit
 
A23-0164
  • ‒ → Pull rubber seal -1- forwards off plenum chamber cover.
  • ‒ Detach plenum chamber cover.
  • ‒ Remove both windscreen wiper arms -2- (marking their positions).
  • ‒ Unclip the scuttle panel trim (see arrows).
 
A23-0163
  • ‒ → Remove the cover of the control unit protective enclosure.
 
N28-0123
  • ‒ → Use screwdriver to carefully prise off securing strap -arrow-.
 
A24-0593

→ To render access to connectors at engine control unit more difficult, engine control unit -1- is bolted to a sheet-metal housing -5- by way of a catch -2- and shear bolts -3- and -4-.
 
A24-0475

Tools required:

  • ◆ → Hot-air blower -1- (from wiring-harness repair set VAS 1978)
  • ◆ Nozzle attachment -2- (also from wiring-harness repair set VAS 1978)
  • ◆ Small, commercially available gripping pliers
Attention:
Heating the thread of the catch also greatly increases the temperature of the shear bolts and sheet-metal housing components. 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).
 
A24-0593

→ The threads of the two shear bolts -Item 4- (which are not bolted to the engine control unit) are coated with a locking fluid. The threads must therefore be heated using the hot-air blower to allow the two bolts to be screwed out.

→ The threads of the two shear bolts which are bolted to the engine control unit -Item 3- are not coated with a locking fluid. The thread in the control unit housing should not and need not be heated (unpermissible heating of the engine control unit).
 
A24-0476
  • ‒ → Make settings on hot-air blower as shown in illustration, i.e. set temperature potentiometer -2- to max. heat output and two-stage air flow switch -3- to position 3.
 
A24-0594
  • ‒ → Heat threads of connector-side shear bolts as shown in illustration for approx. 25 to 30 seconds .
Attention:
Heating the thread of the catch also greatly increases the temperature of the shear bolts and sheet-metal housing components. 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).
 
A24-0595
  • ‒ → Unscrew shear bolts using gripping pliers (see direction of arrow).
  • ‒ The two shear bolts screwed into the control unit do not need to be heated. They can be unscrewed without being heated.
  • ‒ Detach sheet-metal catch from control unit connectors.
 
A10-0762
  • ‒ → Release catch -arrows- and unplug connectors -1- and -2- of control unit.
  • ‒ Take out old engine control unit and fit new one.

Installing

Install in reverse order, paying attention to the following:

The following steps must be performed after connecting new engine control unit:

  • ‒ Activate engine control unit in "Assisted fault-finding" under diagnosis item "Replacing engine control unit".

Vehicle diagnostic, testing and information system VAS 5051 must be used for this purpose.

  • ‒ Protective enclosure must be fitted back on engine control unit. New, genuine shear bolts must be used.

Procedure following interruption of power supply > < Wiring and component check using test box V.A.G 1598/39