Audi Workshop Service and Repair Manuals

The following procedure applies to engine control unitsnot fittedwith a protective metal casing. For engine control unitswithprotective metal casing, refer to=>Page 24-110 .

Removing

• ‒ Connect the vehicle diagnostic, test and information system VAS 5051 and select the vehicle system "01 - Engine electronics". When doing this the ignition must be on.

→ The display on vehicle diagnostic, test and information system VAS 5051 will show the control unit identification and the coding -2-.

• ‒ Always start by calling up and printing out the control unit identification.
• ‒ Switch off ignition.
• ‒ Unbolt windscreen wiper arms.
• ‒ Remove plenum chamber cover and rest it against the windscreen.

Note:

Always make sure that the ignition is switched off before unplugging or fitting the connectors for the engine control unit.

• ‒ Release catches and unplug control unit connectors.

• ‒ → Press back retainer on bracket using a screwdriver, then pull engine control unit towards the front of the vehicle to remove.

Installing

Install in reverse sequence; note the following points:

• ‒ → Bend retainer tab on bracket back into its original position.

The following steps need to be performed after connecting the new engine control unit:

• ‒ Activate the engine control unit via the "Guided fault finding" function (diagnosis object "Renewing engine control unit").

For this step use vehicle diagnostic, testing and information system VAS 5051.

Procedure for replacing an engine control unit with a bolted protective metal casing

Removing

• ‒ Connect the vehicle diagnostic, test and information system VAS 5051 and select the vehicle system "01 - Engine electronics". When doing this the ignition must be on.

→ The display on vehicle diagnostic, test and information system VAS 5051 will show the control unit identification and the coding -2-.

• ‒ Always start by calling up and printing out the control unit identification.
• ‒ Switch off ignition.

• ‒ Unbolt windscreen wiper arms.
• ‒ Remove plenum chamber cover and rest it against the windscreen.

Note:

Item -1- in the illustration shows the engine control unit with protective metal casing.

→ As a deterrent against unauthorised access to the connectors on the engine control unit, the control unit -1- is bolted to a metal casing -4- by means of shear bolts -3- and a locking plate -2-.

The threads of the shear bolts are additionally coated with a thread-locking compound to make them more difficult to remove.

In order to unplug the connectors from the engine control unit (for instance when connecting the test box or replacing the engine control unit), the locking plate -2- must be separated from the protective casing. The required procedure is described below:

The following tools are required:

• ◆ → Hot-air blower -1- (from wiring repair set VAS 1978)
• ◆ A normal (commercially available) vice-grip wrench

Procedure:

→ To avoid damage to wiring or connectors, use heat shields (Items -1- and -2-, consisting of metal plates).
This should protect the connector housing and wiring harness from overheating.

• ‒ → Set controls on hot-air blower as shown in illustration:
  temperature control -2- to maximum heat and two-stage air delivery switch -3- to setting 3.

Note:

In the next step the blower is used to heat the shear bolt in the locking plate. This reduces the effect of the thread-locking compound so the bolts can then be removed more easily.

• ‒ → Apply nozzle -1- of hot-air blower to bolt -2- on locking plate.

Note:

Be particularly careful here because the control unit connectors are very close to this bolt.

• ‒ Switch on the blower and apply heat to the thread for about 20 to 25 seconds.
• ‒ → Apply vice-grip wrench -1- to bolt head -2- and unscrew shear bolt in direction indicated (arrows).

• ‒ For added protection, the locking plate is positioned so that the wrench cannot be turned through one full turn.

Repeat the procedure for the second shear bolt. Be particularly careful here because the control unit connectors are very close to this bolt.

• ‒ After removing the second bolt, you must then remove the windscreen wiper system:

=> Electrical system; Repair group 92; Windscreen wiper system; Removing and installing windscreen wiper system

• ‒ Now pull out control unit complete with metal casing.

With the control unit removed from the vehicle, the locking plate must now be unbolted from the casing. The locking plate must be removed before pulling out the control unit.

→ As a deterrent against unauthorised access to engine control unit -1-, locking plate -2- is bolted to the metal casing by means of shear bolts -3-.

The threads of the shear bolts are additionally coated with a thread-locking compound to make them more difficult to remove.

• ‒ Clamp the control unit in a vice.

The following tools are required:

• ◆ → Hot-air blower -1- (from wiring repair set VAS 1978)
• ◆ A normal (commercially available) vice-grip wrench

Procedure:

• ‒ → Set controls on hot-air blower as shown in illustration:
  temperature control -2- to maximum heat and two-stage air delivery switch -3- to setting 3.

Note:

In the next step the blower is used to heat the shear bolt in the locking plate. This reduces the effect of the thread-locking compound so the bolts can then be removed more easily.

• ‒ → Apply nozzle -1- of hot-air blower to bolt -2- on locking plate.
• ‒ Switch on the blower and apply heat to the thread for about 20 to 25 seconds.

• ‒ → Apply vice-grip wrench -1- to bolt head -2- and unscrew shear bolt in direction indicated (arrows).
• ‒ For added protection, the locking plate is positioned so that the wrench cannot be turned through one full turn.

Repeat the procedure for the second shear bolt.

The engine control unit can now be separated from the metal casing.

• ‒ Take out the old engine control unit and install the new one.

Installing

Installation is performed in the reverse sequence: install metal casing (with locking plate) on engine control unit. Use new shear bolts.

The following steps need to be performed after connecting the new engine control unit:

• ‒ Activate the engine control unit via the "Guided fault finding" function (diagnosis object "Renewing engine control unit").

For this step use vehicle diagnostic, testing and information system VAS 5051.