Emission Control Systems: Tools and Equipment

DIGITAL VOLT/OHM METER (DVOM)
A 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.

LED TEST LIGHT

Do-It-Yourself LED Test Light:

A test light which uses a light emitting diode (LED) will be required to perform some tests. Do not use test lights with incandescent bulbs for testing computer controlled circuits, ECM damage may result. An LED test light can be purchased from your local Audi dealership (part # VAG 1527B or US 1115) 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

BREAK-OUT BOX
Directly probing ECM/TCM connector terminals can result in damaged terminals and create future problems. A special break-out box (VAG 1598) is available from Audi that plug directly into ECM/TCM and harness connectors. There are also Break-out boxes available from other manufacturers that connect to the vehicle. This type of test box allows 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 adapter harness for the application.

SPECIAL TEST HARNESS

Harness Adapter For Checking Differential Pressure Regulator Current:

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 (part # VW 1594).

Self-made Parallel Test Leads:

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.

SCAN TOOL
A Scan Tool is required to access all functions of the on board diagnostic system. Audi specifies the use of the VAG 1551 Scan Tool in all of their diagnostic and repair information. There are some functions of the OBD system that can be accessed with out the VAG 1551 and these are covered in the Testing Procedures. With the use of the VAG 1551 many of the actual values of sensors and settings can be checked. The VAG 1552 scan tool is direct substitute for the VAG 1551 with the exception of printing. The VAG 1552 does not have print-out capabilities. There are other Scan Tools available from other manufactures that may be used to diagnose this system.

REMOTE CONTROL
Several test procedure specify the use of a special remote control VW 1348 to power certain electrical circuits. The remote provides the ability to control the current flow while performing the test. It consists of a switch on a length of wire and a set of harness adapters. The adapters allow for connection to a variety of connector configurations and the switch allows control of power flow.