Component Tests and General Diagnostics

NOTE:
- Test box V.A.G 1598/31 is designed so that it can be connected to the wiring harness for the engine control module and to the engine control module itself at the same time.
- This has the advantage of enabling the engine management system to remain fully operational even with the test box connected (for example, when testing signals while the engine is running).
- The instructions for performing the individual tests indicate whether or not the engine control module itself also needs to be connected to the test box.
- Use the hand multimeter V.A.G 1526 or the multimeter V.A.G 1715 and the diode test lamp V.A.G 1527 for the checks.
- To connect the testers to test box 1598/31, always use the adapter leads from adapter set V.A.G 1594.
- After re - connecting the engine control module, perform adaptation of engine control module to throttle valve control module.

WARNING! To prevent damage to the electronic components, switch to the respective measuring range before connecting the test lead and observe the test requirements.

- Switch off ignition.
- Remove cover of protective housing for control modules.





- Carefully lever off the retainer bar with a screwdriver - arrow
- Then release connectors on control module and pull off.





- Connect test box V.A.G 1598/31 to wiring harness connector. Also connect the Ground clamp on the test box (not shown in the illustration) to the battery negative terminal. The instructions for performing the individual tests indicate whether or not the engine control module itself also needs to be connected to the test box.
- Carry out test as described in the repair instructions.
- Disconnect harness connector at cruise control switch.
Wire connection should be checked for short circuit to B+, short circuit to Ground and open circuit.
- Check wire connection according to wiring diagram.
- Repair open circuit or short circuit if necessary.
If wire connection is OK, cruise control switch must be replaced.