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 VCDS?
VCDS (VAG-COM Diagnostic System) 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) 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
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
The current Release of VCDS
contains the TDI Timing Checker.
See this page for more
This procedure does NOT apply to the
Engine has to be warm (coolant above
Go to Engine Measuring Block 000 (Group 004 for V6 TDI)
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
It is strongly discouraged to set
your timing outside of the specification!
Special adaptations: Login code 12233:
These procedures do NOT
apply to the PD engines, which use a completely different type of EGR system and for
which there is no known modification. !
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
This is done at your own risk!
Note that the EGR setting is for off-road use
[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
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
Donít 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