Introduction

INTRODUCTION:
This section covers "generic" scan tool diagnosis and repair with ANY available OBD II scan tool, using Address Word 33.

Starting with m.y. 1996, U.S. government regulations require 2nd generation On Board Diagnosis (OBD II) systems on vehicles sold in the United States, with Diagnostic Trouble Codes (DTC) memory that is accessible to technicians without using the manufacturer's proprietary scan tool, such as VAG 1551.

For specific emissions-related malfunctions, the engine management system must generate and store a specific description of each malfunction (identified by a standard "P" code) in the Engine Control Module (ECM).

P-codes and descriptions can be retrieved using ANY available OBD II scan tool, including the Volkswagen VAG 1551 Scan Tool operating in "generic" mode. This information can then be used to troubleshoot and repair emissions-related malfunctions.

This scan tool described here is the Volkswagen/Audi VAG 1551 Scan Tool operating in "generic" mode. For the workshop equipped with the VAG 1551, this section offers alternatives for system diagnosis and repair, emphasizing on-vehicle troubleshooting rather than the full range of VAG 1551 Scan Tool Output Diagnostic Test Mode (DTM) and Measuring Value Block functions.