VAG On-Board Diagnostics

NOTE: If VAG SELF-DIAGNOSIS (VAG ON-BOARD DIAGNOSTIC) display does not appear on scan tester, check DLC terminals for battery voltage and ground. Upper terminal should have battery voltage, bottom terminals serve as ground.

Ensure battery voltage and fuse No. 22 are okay. Ensure engine/transmission ground connections are okay. Ground lead is located near or below intake manifold.
Connect Scan Tester (VAG 1551) to Data Link Connectors (DLC) located below A/C-heater control panel. Attach Black connector first, wait for VAG ON-BOARD DIAGNOSTIC display, then connect White connector. DO NOT connect scan tester Blue connector.
Turn ignition on or start engine depending on function being selected. See appropriate SELECTABLE FUNCTIONS table. Press "1" button to select RAPID DATA TRANSFER function.
Press "0" and "1" buttons to select ENGINE ELECTRONICS function. Press "Q" button to enter input. Electronic Control Module (ECM) identification will be displayed on scan tester.
If CONTROL MODULE DOES NOT ANSWER (RESPOND) message is displayed, press HELP button to print a list of possible causes. With scan tester in RAPID DATA TRANSFER function, press right arrow button. Press "00" to "09" buttons to select desired function. Press "Q" button to enter input.

SELECTABLE FUNCTIONS ⁽¹⁾

Function

Ignition On

Engine On

02 (Read DTC Memory)

⁽²⁾ X

03 (Output Diagnostic Test Mode)

N/A

04 (Initiate Basic Setting)

N/A

⁽³⁾ X

05 (Erase DTC Memory)

N/A

06 (End Data Transfer)

08 (Read Measurement Block)

09 (Read Individual Measurements) ⁽⁴⁾

⁽¹⁾	Press HELP button at any time to obtain additional scan tester operating instructions.

⁽²⁾	With ignition on, only if engine does not turn over (start).

⁽³⁾	And select display group "01". End basic setting function only if coolant temperature is more than 185°F (85°C).

⁽⁴⁾	Currently used only during vehicle manufacture.