SEAT Workshop Service and Repair Manuals

Removing and installing engine control unit t  Removing → Anchor. t  Installing → Anchor. Consult the equivalence table for tools and equipment according to applicability among Seat / VW / Audi / Skoda → Chapter. Special tools and workshop equipment required

t  Pneumatic sabre saw -VAG 1523B-

t  Hot air gun from cable repair set -VAS 1978B-, see equivalent → Anchor t  Application nozzle from the wiring harness repair set -VAS 1978B-   Note If you wish to renew the engine control unit, connect the → Vehicle diagnostic, testing and information system VAS 5051 and carry out the guided function „Renew control unit“. Removing –  Switch ignition OFF.   Note

t  The engine control unit -1- is bolted to the protective housing -5-. To make it more difficult to unscrew the shear bolts -4- for locking plate -2-, their threads have been coated with locking fluid. t  The metal casing 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). –  Remove wind moulding → Bodywork, exterior fitting work; Rep. gr.50.

–  Unscrew bolts -arrows- from cover on electrical box in water reservoir.

–  Carefully lever off retaining strap with a screwdriver -arrow-. –  Take engine control unit out of retainer.

Using the body saw -VAG 1523B- make a groove on the heads of the shear screws for inserting a screwdriver.   Note t  The groove must be wide enough in order to be able to screw out the screws using an appropriate screwdriver. t  The thread on the shear screws can been treated with a threadlocker. For making sure that unscrewing is easier, you can warm the shear screws using the Hot air blower -VAS 1978/14A-. In doing so, take care that no bordering cables, plugs or components are damaged! .   WARNING The threads of the two shear screws which are screwed into the engine control unit are not secured with locking fluid. Do not apply heat to the threads in the control unit housing; this is not necessary and would cause overheating of the control unit. The threads of the shear screws which are not screwed into the engine control unit are not secured with locking fluid. To unscrew these bolts, the threads must therefore be heated with the hot-air blower. To ensure that damage (burning) is not caused to the cables and connectors as well as insulation and control units, the following steps must be observed in all cases: Remember the instructions for using the hot-air gun.

To prevent access to the engine control unit plug connectors, the engine control unit -1- is screwed on with an arresting element -2 and 5- and tear-off screws -3 and 4-. Carry out the adjustments on the hot air blower -4- as described below:

–  Turn temperature setting potentiometer -2- to maximum heat output (600°C). –  Set two-stage switch for volume of air -3- to position 3.   WARNING The threads of the two shear bolts -3- which are screwed into the engine control unit are not secured with locking fluid. Do not apply heat to the threads in the control unit housing; this is not necessary and would cause overheating of the control unit.   Note

Then use hot air blower to heat shear screws -4-. This reduces the strength of the threadlocker on the thread of the breakaway bolts to make them easier to remove.   WARNING Heating the thread of the locking plate also heats up the shear bolts and parts of the metal housing. Risk of burn injuries! It is also important to ensure that only the thread is heated and none of the surrounding components if at all possible. If necessary, cover these parts.

–  Bring the nozzle of the hot-air gun up to the breakaway bolt on the lock. –  Connect hot air gun and heat bolt approx. 20 to 25 seconds.

–  Unscrew the shear screws using a screwdriver. –  Detach metal locking plate from control unit connectors.

–  Loosen connector locks in direction of -arrows- and disconnect connector -1 and 2- from engine control unit. –  Remove the engine control unit -J623-. Installing Installation is carried out in reverse order, noting the following: –  Clean threaded holes for shear bolts to remove any residue from locking fluid. The threads can be cleaned with a thread tap. –  Fit connectors and lock in position. –  Push protective housing over engine control unit. –  Separate the protective casing from the engine control unit. –  Use new breakaway bolts. –  Tighten the shear screws evenly, until the screw heads break off. l  Tightening torque for bolts securing cover of electronics box: 3.5 Nm. The procedure required after connecting the new engine control unit is described in the Guided fault-finding or Guided functions. –  Replace engine control unit in „guided functions“ under „J623 - Replace engine control unit: “ Activate → Vehicle diagnostic, testing and information system VAS 5051 further work stages. –  The injector delivery calibration and the injector voltage calibration must additionally be re-adapted in the engine control unit -J623- after the control unit has been renewed (these functions influence engine power and exhaust emissions).