SEAT Workshop Service and Repair Manuals > Leon Mk1 > Power unit | 4LV Injection and Ignition System | Mixture preparation system, electronic inj.,Gas | Supplementary signals: testing | Data bus: testing

Test process

–	Switch off the ignition.

–	Free the connectors from the engine control unit and remove them.

–	Connect test box -V.A.G. 1598/31- to the engine control unit, without connecting the wiring harness of the control unit.

–	Test the central matching resistor incorporated in the engine control unit.

–	For this purpose, test the resistance between female contacts 58 + 60 Target value: 60...72 Ω

If the resistance value is not within the target range:

–	Replace the engine control unit → Anchor.

If the resistance value is within the target range:

–	Detach the test box -V.A.G. 1598/31- from the engine control unit.

–	Connect the test box -V.A.G. 1598/31- to the wiring harness of the engine control unit.

–	Test the wiring of the CAN data bus for short circuits between wires:

–	For this purpose, test the resistance between female contacts 58 + 60 of the test box: Target value: ∞ Ω

If the target value is reached (the wiring has no short circuits between wires):

–	Following the wiring diagram, test the wiring to the components of the CAN data bus for short circuits to positive or earth or an open circuit: → Current flow diagrams, Electrical fault finding and Fitting locations

If the target value is not reached (the wiring has a short circuit between wires):

–	Eliminate the wiring fault following the wiring diagram: → Current flow diagrams, Electrical fault finding and Fitting locations

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