Audi Workshop Service and Repair Manuals

Removing and installing engine control unit   Note

t  The engine control unit is bolted to its protective housing. To make it more difficult to unscrew the shear bolts -arrows-, their threads have additionally been coated with locking fluid. t  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). Special tools and workshop equipment required

t  Hot air blower, 220 V/ 50 HZ -VAS 1978/14--item 1- t  Shrink element for hot air blower -VAS 1978/15--item 2- t  Vice-grip pliers -3- (commercially available) Removing –  When renewing the engine control unit, select the test procedure / function “Renew engine control unit” in “Guided Functions” → Vehicle diagnosis, testing and information system VAS 5051. –  Remove windscreen wiper arms → Rep. Gr.92.

–  Unclip washer jets -arrow-. –  Push washer jet through assembly opening back into plenum chamber, leaving hoses connected.

–  Pull off rubber seal -1- on plenum chamber cover. –  Detach plenum chamber cover -2-.   Caution The following procedure must be followed exactly to prevent any damage (burning) to wiring, connectors, insulation and control units. Observe operating instructions for hot air blower.

–  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”.   Note t  Then use hot air blower to heat threaded holes in protective housing into which shear bolts have been screwed. This reduces the inhibiting action of the locking fluid on the shear bolt threads and makes it easier to unscrew these bolts. t  Cover up all painted parts to avoid any damage caused by hot air blower or vice-grip pliers.   WARNING Parts of the protective housing will become very hot as a result of heating the shear bolts. Take care to avoid burns. Try to ensure that only the thread is heated and none of the nearby components. These should be covered if necessary.

–  Carry out the following operations on the two shear bolts -arrows-, one after the other. –  Place the nozzle of the hot air blower close to the shear bolt on the protective housing. –  Switch on the hot air blower and heat the bolt for approximately 20 ... 25 seconds. –  Then grasp the bolt head with the vice-grip pliers and unscrew the shear bolt. –  Take off the protective housing.

–  Release and unplug front connector -2- on engine control unit. –  Release retaining clip -arrow-. –  Pull engine control unit -1- out of bracket. –  Release and unplug rear connector on engine control unit.   Note When the engine control unit is disconnected, the learnt values are erased but the contents of the fault memory remain intact. Installing Installation is carried out in the reverse order; note the following: –  Protective housing must be fitted back on engine control unit. –  Clean threaded holes for shear bolts to remove any residue from locking fluid. This can be done using a thread tap. –  Use new shear bolts. –  Install windscreen wiper arms → Rep. Gr.92. After installing a new engine control unit, the following operation must be performed: –  Activate engine control unit in “Guided Functions” under the test procedure / function “Renew engine control unit” → Vehicle diagnosis, testing and information system VAS 5051.