Computers and Control Systems: Tools and Equipment
DIGITAL VOLT/OHM METERA digital volt/ohm meter (multi-meter), with a minimum 10 megohms internal impedance, must be used when testing electronic circuits in automotive computer controlled systems (see VEHICLE DAMAGE WARNINGS under SERVICE PRECAUTIONS).
LED TEST LIGHT
Do-It-Yourself LED Test Light:
A test light which uses a light emitting diode (LED) may be required to perform some tests. Do not use test lights with incandescent bulbs for testing computer controlled circuits, ECU damage may result. An LED test light can be purchased from your local Audi dealership (part #VAG1527B) or one can be constructed with parts available from any electronics supply store (see diagram). The Audi special tool uses two LEDs and depending on the polarity of connections being tested, one or the other will illuminate (DC circuits), or if testing an AC circuit, both LEDs will flash alternately
ECU TEST CONNECTORS
Directly probing ECU connector terminals can result in damaged terminals and create future problems. Special test connectors are available from Audi that plug directly into ECU and harness connectors. These connectors allow safe testing of circuits where limited access to wiring harness connectors makes testing difficult. Connectors are not universal for all models. Be sure to use the proper connector for the application (consult your Audi dealer).
Harness Adapter For Checking Differential Pressure Regulator Current:
Self-made Parallel Test Leads:
Some test procedures require the use of special test leads to gain parallel access to circuits for testing without piercing or splicing wires. These connectors are available from your Audi dealer. Self made connectors can be an inexpensive alternative. Be sure to use the proper size wire terminals for the device or connector you wish to test. In cases where you need to connect several test leads to a single device or harness connector, use color coded wire for easy identification of which terminal is being tested and be sure ends of leads are not touching each other, insulate terminals if necessary.