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VAG-COM

TDI Fest 2002

TDI-Specific Procedures



Summary

• Introduction

• Basic operations

• Checking the air system

• Setting the injection timing

• Special adaptations• Performance Measurement

• More Information



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)



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.)



Note

• The following advanced operations are

intended for an A4 TDI (ALH engine).

Expect some variations if you have anA3/B4 car (A3 Jetta, Passat)



Air system part I: MAF

• Go into Engine measuring block 003

• Start Logging data

• In a high gear (4th/5th), give full throttle

from 1500-2000 rpm up to 3500-4000rpm.

• Find and Open the Log file in Windows

Explorer

• Graph MAF specified/actual/rpm -vs- time

in Excel



Checking the MAF - continued• The MAF is OK if the actual value is more

than 850-900 mg/h at 3000 rpm.



Turbo - continued• On a stock vehicle, one should see a spike

at 2.1 bar quickly regulated at 1.9 throughthe whole rpm range



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)



10

15

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25

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35

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45

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55

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50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210

Fuel temp (9)

I n j a d v a

n c e (

2 )

Ret. timing

Med.timing

Adv. timing



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 athttp://pics.tdiclub.com/members/ericmaurier/timing.xls



Special adaptations: Login code

• To perform the following adaptations

(except idle) you need to use the Login

function. Enter 12233 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...



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 adaptationchannel 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.



Channel 2: idle speed

• No login required

• To increase idle speed, increase the value

and vice-versa



Channel 3: EGR

• To decrease the EGR rate, increase thenumber to the highest possible value

(typically 33768)

• This will prevent/slow down the intakemanifold clogging problem and reduce

smoke

• Though the MAF at idle is still withinspecifications (370 mg/h) do not use this

adaptation on the road :-)



Channel 4: start of injection

• This channel commands the start of injectionover 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!



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



Performance Measurement

• “Butt Dyno”



More Info

• 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

• Visit our website:

WWW ROSS-TECH COM

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