![[B] Bentley Publishers — Automotive Reference](https://bentleypubs.com/wp-content/themes/bentleypubs/images/bp-banner-234x60-bookblue.svg)
Repair Manuals · DTCs · TECH · VIDEOS · Service Training · Owner's Manuals · DVDs · History
Reading what the car is telling you. Audi cars of model year 1996 and later report OBD II P-codes — enter one below. The factory training on engine management, the tools, and the Audi technical library follow.
Decode an OBD II fault code (1996 and later)
OBD II, model year 1996 and later: enter the P-code your scan tool displays (P0420) or the five-digit factory number (17828). Cars of 1990–1995 use the earlier system — see the Volkswagen Scan Tool Companion.
The code page: any of 774 codes, with the P-code key →
How a P-code is built — the full key
First digit — the system
- Pxxxx — powertrain
- Bxxxx — body
- Cxxxx — chassis
- Uxxxx — future systems
Second digit — who defined it
- P0xxx — Government required codes
- P1xxx — Manufacturer codes for additional emission system function; not required but reported to the government
Third digit — the subsystem
- Px1xx — measurement of air and fuel
- Px2xx — measurement of air and fuel
- Px3xx — ignition system
- Px4xx — additional emission control
- Px5xx — speed and idle regulation
- Px6xx — computer and output signals
- Px7xx — transmission
- Px8xx — transmission
- Px9xx — control modules, input and output signals
The fourth and fifth digits designate the individual components and systems.
How to connect a scan tool · How a P-code is built · Scan tools
Fault codes
- Audi diagnostic trouble codes — any of 774 codes, with the P-code key
Factory service training on diagnosis
Engine management reference
Audi technical library
The Audi technical library → — articles by car, maintenance schedules, and the fault-code lookup.
Scan tools
Scan tools and where to get them — factory and aftermarket, with the supplier list as published with the 2001–2004 code list (check a supplier before ordering) — and how to connect one.
Facebook · 
YouTubeBentley Publishers, Cambridge MA 02138-1804 USA © 2026 Robert Bentley, Inc. All rights reserved. Bentley Publishers, BentleyPubs, and Linnaean Press are trademarks of Robert Bentley, Inc. Website by The Information Foundry.
pubs-wp r1 v002 · 2026-10-06