TDI VAG-COM Info
Posted  16 Apr. 2003

Ross-Tech is not responsible for any damage or problems that may result from following these instructions. They are to be used at your own risk.

Note: These are useful procedures that may or may not work on your particular vehicle. Consult a Factory Repair Manual before doing any modifications to your car.

Q: What is VAG-COM?

VAG-COM is Windows-based software that allows a PC to act as a diagnostic tool for VW/Audi/SEAT/Skoda vehicles.

Q: That's great, so what can I do with it?

Well, here is a partial list:

01 Control Unit Info (means you can read your ECU's part number without pulling it out)
02 Read Fault Codes (aka DTC's, you can find out why your MIL - aka CEL - is on)
03 Output Tests (as part of troubleshooting procedures, you can turn on various actuators)
04 Basic Settings (lets you set readiness, perform various functions)
05 Clear Fault Codes (lets you get rid of the DTC's) 
07 Code Module (lets you to set up the "BIOS" of a control module)
08 Measuring Blocks (lets you measure various running parameters) 
10 Adaptation (lets you adapt or introduce components to one another)
11 Login (needed to access certain functions)
15 View Readiness (checks to make sure self-tests have been done, only applies to gassers)
Data Logging  (you can save measuring blocks to a file - up to 3 groups of 4 at a time)
7-Digit PINs (used for new keys, instrument clusters, or new ECU's)

Q: So, specifically, as relates to my TDI, what can I do with it?

Note: The following advanced operations are intended for a stock 90-hp A4 TDI (ALH engine). Expect some variations if you have an A3/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 2500 rpm up to 3500rpm.
• Find and Open the Log file in Windows Explorer
• Graph MAF actual -vs- rpm in Excel
• The MAF is OK if the actual value is at least 850-900 mg/h at 3000 rpm.

Air system part I: Turbo

• Go to Engine Measuring Block 011
• Start Logging the data
• In a high gear (4th/5th) give full throttle from 1500-2000 rpm to 3500-4000 rpm
• Find and Open the Log file in Windows Explorer
• In Excel graph actual/requested boost -vs- rpm
• On a stock vehicle, one should see a spike at 2.1 bar quickly regulated at 1.9 through the whole rpm range

Setting Injection Timing:

The current Release of VAG-COM contains the TDI Timing Checker. See this page for more information.

• 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

• Specification is within the shaded area between the blue and red lines

• To slightly advance timing, you need to be in the upper portion of the shaded area.

• Setting is done mechanically, slightly rotating the pump shaft once its three screws have been loosened.

• It is strongly discouraged to set your timing outside of the specification!

Special adaptations: Login code 12233:

• 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...

[Select]
[01 - Engine]
[Login - 11]
Enter 12233 to activate special adaptations,
[Do It!]

[Adaptation - 10]
Enter the "channel number" below to select each channel.
Put in the suggested value(s) in "new value".
[Test]
Observe the "test value" field to make sure the adaptation setting is acceptable.
[Save]

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.

Channel 2: idle speed

• No login required
• The stock adaptation value should be 32768 (corresponds to 903 rpm).
• Increase or decrease this to change idle speed.

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 :-)
• Again, this EGR setting is for off-road use only !!!

Channel 4:

• Don’t mess with it!

Channel 5: starting conditions

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

Activating Cruise Control on a new ECU (DBW):

Factory fresh ECU's often come with cruise control de-activated.

[Select]
[01 - Engine]
[Login - 11]
Enter 11463 to activate cruise control
[Do It!]

Installing a new ECU:

Immobilizer 2 info (2000-2001)

Immobilizer 3 info (2002+)

Q: Where can I find specific info about my car?

First off, the best source is the aforementioned Factory Repair Manual. See here for some useful links for particular vehicles:

VW & Audi Application Charts

And of course, everyone with a TDI should frequent Fred's TDI Forums, aka TDIClub.com:

TDI Club  Specifically the TDI Club FAQ

For TDI questions, please contact eric@ross-tech.com