1. TDI Fest 2002 TDI-Specific Procedures
VAG-COM
TDI Fest 2002
TDI-Specific Procedures

2. Summary Introduction Basic operations Checking the air system
Setting the injection timing
Special adaptations
Performance Measurement
More Information

3. Introduction: what is VAG-COM?
Emulates the dealers’ VAG-1551 and VAG-1552 tool
Uses Windows-based PC (100 MHz recommended)
Used by enthusiasts, general repair ships, transmission shops, locksmiths, dealerships
Uses VAG protocol (separate from OBD-II)

4. Basic Operations Read/Clear/Print Fault Codes (DTC’s)
Diagnose MIL (Check Engine Light - CEL)
Monitor/Log/Print Measuring Blocks for various running parameters
Recode convenience items (power locks, radio, etc.)

5. Note
The following advanced operations are intended for an A4 TDI (ALH engine). Expect some variations if you have an A3/B4 car (A3 Jetta, Passat)

6. Air system part I: MAF Go into Engine measuring block 003
Start Logging data
In a high gear (4th/5th), give full throttle from rpm up to rpm.
Find and Open the Log file in Windows Explorer
Graph MAF specified/actual/rpm -vs- time in Excel

7. Checking the MAF - continued
The MAF is OK if the actual value is more than mg/h at 3000 rpm.

8. Air system part II: Turbo
Go to Engine Measuring Block 011
Start Logging the data
In a high gear (4th/5th) give full throttle from rpm to rpm
Find and Open the Log file in Windows Explorer
In Excel graph actual/requested boost/rpm vs time

9. Turbo - continued
On a stock vehicle, one should see a spike at 2.1 bar quickly regulated at 1.9 through the whole rpm range

10. Setting the injection timing
Engine has to be warm (coolant above 85ºC)
Go to Engine Measuring Block 000
Switch to Basic Settings
Take note of the values in fields 2 (timing) and 9 (fuel temp)
Report in the following graph (also in the Bentley manual)

12. Setting timing-continued
Specification is between the blue and red lines
To slightly advance timing, you need to be in the upper portion of the graph. Setting is done mechanically, slightly rotating the pump sprocket once its three screws have been loosened.
It is strongly discouraged to set your timing outside of the specification!
Graph is available at

13. Special adaptations: Login code
To perform the following adaptations (except idle) you need to use the Login function. Enter as a Login code.
Misuse of some of the adaptations can lead to engine failure. This is done at your own risk!
Note that the EGR setting is for off-road use only...

14. Channel 1: injected quantity
Check the injected quantity at idle, engine warm and all power consuming devices turned off. Specification is 2.5 to 9 mg/h.
To change the amount of injected fuel perceived by the ECU, go to adaptation channel 1.
If you have driveability problems, you may want to increase it to 3-4 mg/h.
For slightly improved throttle response, you may try to decrease the value.

15. Channel 2: idle speed No login required
To increase idle speed, increase the value and vice-versa

16. Channel 3: EGR
To decrease the EGR rate, increase the number to the highest possible value (typically 33768)
This will prevent/slow down the intake manifold clogging problem and reduce smoke
Though the MAF at idle is still within specifications (370 mg/h) do not use this adaptation on the road :-)

17. Channel 4: start of injection
This channel commands the start of injection over the whole operating range of the engine, including at full load. Advanced timing there may lead to severe damage to the engine because of the increased combustion pressure.
It is in no way a substitution for the mechanical pump setting seen previously
In a nutshell: don’t mess with it!

18. Channel 5: starting conditions
Though undocumented, this channel effects the injected quantity the ECU allows when cranking
You may want to experiment with it as a temporary fix for bad-start problems

19. Performance Measurement
“Butt Dyno”

20. More Info Visit our website: WWW.ROSS-TECH.COM
Mk IV Lock/Unlock Horn/Flash:
[Select] [46 - Cent. Conv.] (35 - Cent. Locking for manual window cars) [Adaptation - 10] Channel (03..08) Adaptation Value (1 = on, 0 = off) [Save] Channel 03 Auto Lock Channel 04 Auto Unlock Channel 05 Unlock, horn sounds Channel 06 Lock, horn sounds Channel 07 Unlock, turn signals flash Channel 08 Lock, turn signals flash
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