Wire and Component Test at Engine Control Module using VAG 1598/31: Notes

Fig 1: V.A.G 1598/31 Test Box

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NOTE:

Test box VAG1598/31 is designed so that it can be simultaneously connected to the wiring harness at the Engine Control Module (ECM) and also to the ECM itself.
This is advantageous because electronic engine control remains fully functional (e.g. measurement of signals with engine running) when the test box is attached.
Relevant test procedures note whether Engine Control Module (ECM) should also be connected to the test box or not.
Use the following for the test: portable multimeter VAG1526 or the multimeter VAG1715 and the voltage test lamp VAG1527.
Always use adapter cables from connector test kit VAG1594 for connecting special tools to the test box VAG1598/31.

CAUTION: To avoid damaging electronic components, set measuring range before connecting test leads and observe all test requirements.

VAG1598/31, Connecting

Switch ignition off.
Remove right cover from plenum chamber.

Fig 2: Engine Control Module (ECM) Bolts

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Open both bolts (- arrows -) and remove Engine Control Module (ECM) toward front.

Fig 3: ECM, Locking Mechanism, Screws And Anti-Theft Housing

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To complicate accessibility to the harness connectors at Engine Control Module (ECM), Engine Control Module (ECM) - 1 - is screwed to a protective housing - 4 - via a locking mechanism - 2 - and snap-off screws - 3 -.

The thread of the snap-off screws is coated with locking compound to additionally complicate removal of the snap-off screws.

To be able to disconnect harness connectors from Engine Control Module (ECM) (e.g. when connecting test box or when replacing Engine Control Module), Engine Control Module (ECM) must be removed from protective housing. This procedure is described in the following.

Required Equipment

Fig 4: Heat Gun, Adapter Nozzle And Pliers

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Heat gun - 1 - (from Wiring Harness Repair Kit VAS1978)
Attachment nozzle - 2 - (also from Wiring Harness Repair Kit VAS1978)
Standard locking pliers

Procedure

CAUTION: To avoid damage (burning) of wire connections and harness connectors, insulation and control modules, the following work steps must be adhered to exactly! Observe operating instructions of heat gun.

Fig 5: ECM, Locking Mechanism, Screws And Anti-Theft Housing

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"Flip" Engine Control Module (ECM) with protective housing in direction of engine compartment so that the locking mechanism (- 2 - in illustration) becomes visible, place a clean rag below the Engine Control Module (ECM) with protective housing.

Fig 6: Performing Adjustments On Hot Air Gun

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Perform adjustments on heat gun as shown in illustration, i.e., potentiometer for temperature selection - 2 - to maximum heat output and the two-stage switch for air flow - 3 - to position 3.

NOTE:

Next, the thread of locking mechanism in which the snap-off screws are threaded in are heated using the heat gun. This step lowers the inhibition effect of the locking compound on the thread of the snap-off screws, to ease the removal of the snap-off screws.

CAUTION: When heating threads of locking mechanism, snap-off screws and components of protective housing are also heated intensely. Do not burn yourself on them! Also make sure that only the thread is heated if possible and no other components in the vicinity are heated. Cover these as necessary.

Fig 7: Nozzle Of Heat Gun Guided To Locking Mechanism Threads So That Nozzle "Encloses" Threads

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Guide nozzle - 1 - of heat gun onto locking mechanism thread so that the nozzle "encloses" the thread. Let nozzle make contact steadily on upper end of protective housing.
Switch on heat gun and heat thread for approx. 20 to 25 seconds.

Fig 8: Grabbing Screw Head And Removing Snap-Off Screw Using Locking Pliers

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Then clamp bolt head - 2 - using locking pliers - 1 - and remove snap-off screw in direction of (- arrow -).

Procedure for the second snap-off screw is exactly the same. Be especially careful, because the control module connectors are located in the immediate vicinity.

Fig 9: Nozzle Of Heat Gun Guided To Locking Mechanism Threads Again So That Nozzle "Encloses" Threads

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Guide nozzle - 1 - of heat gun onto locking mechanism thread again so that the nozzle "encloses" the thread. Let nozzle make contact steadily on upper end of protective housing.
Switch on heat gun and heat thread for approx. 20 to 25 seconds.

Fig 10: Grabbing Screw Head And Removing Snap-Off Screw Using Locking Pliers

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Then clamp bolt head - 2 - using locking pliers - 1 - and remove snap-off screw in direction of - arrow -.

Now Engine Control Module (ECM) can be detached from protective housing.

Disengage connectors from Engine Control Module (ECM) and then disconnect the connectors.

Fig 11: Connecting Test Box V.A.G 1598/31 To Connector On Wiring Harness

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Connect test box VAG1598/31 to connector of wiring harness. Ground (GND) clip must be connected to Ground (GND). Relevant test procedures note whether Engine Control Module (ECM) should also be connected to the test box.
Perform test as described in relevant repair sequence.