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Reading what the car is telling you. Two eras, two kinds of code: cars of model year 1996 and later report OBD II P-codes — enter one in the decoder below; 1990–1995 cars carry the first-generation system, whose codes and data are the subject of the Scan Tool Companion. The books, the factory training, the tools and the articles and videos on the work 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
The diagnostic books
Fault codes
- Volkswagen diagnostic trouble codes — any of 774 codes, with the P-code key
Factory service training on diagnosis
Engine management reference
Volkswagen technical library
The Volkswagen 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.
Technical articles on diagnosis
- VW.DTC.16684 (P0300) - Jetta, Golf, GTI 1999 - 2006, R32 2004 — Volkswagen A4
- VW Golf Jetta New Beetle DTC P1355, P1358, P1361, P1364 - Fix — Volkswagen A4
- DTC Codes — Volkswagen A4
Videos on diagnosis
Volkswagen Evaporative Emission Systems (EVAP) - Operation and Testing - Diagnosing - DIY Repair
VW Golf Jetta New Beetle (A4) 2002-2004 - DTC fault code P1355, P1358, P1361, P1364 - DIY Repair
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