Engine Control Module -J623-

WARNING: This page is about a different variant/trim than selected.

Special tools and workshop equipment required

Heat Gun 220 V/50 Hz VAS 1978/14A with Nozzle Attachment from the Wiring Harness Repair Kit VAS 1978 B
Small Commercially Available Locking Pliers

NOTE:

Some engine control modules are not equipped with a protective housing. The removal and installation of the protective housing depends on the engine and transmission combination.

The engine control module (ECM) -1- is bolted to a protective housing -5-. To make removing the shear bolts -4- for the retaining tabs -2- more difficult, the threads are coated with locking compound.

Fig 1: Identifying Engine Control Module (ECM), Protective Housing, Retaining Tabs & Shear Bolts

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To disconnect the connectors from the ECM (for example to connect the test box or to replace the ECM), the metal housing must be removed.

Removing

-- If the engine control module was replaced, select diagnostic object "replacing engine control module " in "guided functions ".

-- Turn the ignition and remove the ignition key.

-- Pull the plenum chamber cover rubber seal in front of the nut -1- slightly.

Fig 2: Disengaging Wiring Harness

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-- Disengage the wiring harness -2- at the mounts -A-.

-- Remove nut -1-.

-- Remove the filler neck -3- with the filler tube from the washer fluid reservoir and the opening in the body.

-- Remove the bolts -arrows- and the cover from the E-box.

Fig 3: Removing E-Box Bolts & Cover

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-- Release the retainers -A arrows- and remove the ECM -arrow B-.

Fig 4: Location Engine Control Module (ECM) -J623-

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The ECM -1- is secured in a metal housing -5- with retaining tabs -2- and shear bolts -3 and 4- to make it harder to access it.

Fig 5: Identifying Engine Control Module (ECM), Protective Housing, Retaining Tabs & Shear Bolts

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The threads of the shear bolts -4- (that are not screwed into the ECM) are coated with a locking compound. For this reason, the threads must be heated with the heat gun to remove both bolts.

The threads of both shear bolts -3-, that are screwed into the ECM, are not coated with a locking compound. The threads in the ECM housing must not be heated and do not require to be heated (unintentional heating of the ECM).

Fig 6: Identifying Engine Control Module (ECM), Protective Housing, Retaining Tabs & Shear Bolts

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-- Set the adjustment on the heat gun as shown in the illustration, with the temperature potentiometer -2- set to maximum heat and the two-stage airflow switch -3- set to level 3.

Fig 7: Identifying Controls For Temperature Adjustment And Air Quantity

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WARNING:

By heating the threads, the retaining tabs, shear bolts and parts of the metal housing become very hot. Do not burn yourself on this! Make sure that only the threads are heated as much as possible, and not any of the surrounding parts. Possibly cover these parts.

-- Warm threads on connector-side shear bolts for approximately 25 to 30 seconds.

Fig 8: Using Heat Gun To Direct Heat Gun Nozzle At Shear Bolt Of Retaining Tab

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-- Remove shear bolts with locking pliers (see direction of -arrow-).

Fig 9: Identifying Locking Pliers And Shear Bolt

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-- The shear bolts installed in the ECM do not need to be heated for removal. They can be removed without heat.

-- Disconnect metal retainers from the ECM connectors.

-- Disengage the connectors from the ECM and disconnect the connector.

-- Remove old ECM and install the new ECM.

Installing

Install in reverse order of removal.

-- After that, the ECM must be equipped with the metal retainer.

-- Clean threaded holes for shear bolts of locking compound residue. Cleaning can be performed with a thread cutter (tap).

-- Always use new shear bolts.

Tightening specification: screws for the E-box cover: 3.5 Nm

Perform the following step after installing a new engine control module:

-- Activate the engine control module in "guided functions " under "replace engine control module". Use a vehicle diagnosis tester for this.