Guided Fault Finding

Guided Fault Finding 02E, 6 Speed Direct Shift A/T
Before beginning any service work, the cause of damage should be pinpointed using "Guided Fault Finding".





The Guided Fault Finding is performed using Vehicle Diagnosis, Testing and Information System VAS 5051.

General notes about Fault Finding

Thoughts before Fault Finding
You should try to create a logical fault finding process.





- Make yourself aware of what kind of complaint is occurring and what fault finding possibilities you have. Finding faults without a logical fault finding process would - be magic - and does not lead to success.





^ It must also be clear: You should not find faults that others have already found and recognize. Try to see if your problem already had a solution described in Technical Problem Solving.
^ It can also be helpful to be acquainted with the DTC entries from other control modules. Always interrogate all control modules. Also, have the BUS topic in mind during fault finding. For example, in an instance like this.

Information on "control module behavior when there is a malfunction" in the transmission
The control module works with sophisticated software. This software has the ability to execute electrical functions, monitor and control within milliseconds. Everything modern transmission electronics have going for them is located in this control module. This should also be considered during troubleshooting.

However, no electronics can do what they were not designed to do. Likewise, it is not possible to detect electronically, for example, where the transmission housing is leaking and oil is escaping. However, it is possible to detect the effects of low oil. A failure in "gear monitoring" would be recognized causing the control module to respond that both clutches are open (no traction).

You should know this during troubleshooting and also when working with the Volkswagen tester. It is possible that the cause for the malfunction might not be found during Guided Fault Finding. Aside from software that makes it possible for the transmission to operating, much was also done to protect the transmission in case of a malfunction (safety functions). And so, when necessary, malfunctions are saved and a replacement program is started.

Control module behavior during a malfunction
If a component in the transmission malfunctions, the control module reacts with a replacement function. In order to protect the transmission as much as possible, 4 malfunction reactions are differentiated:
1. The malfunction is so minor that it is possible to continue driving with a replacement program while maintaining driving safety. The driver is not notified of this via Selector Lever Transmission Range Display Y5. The display shows the selector lever position normally. When can changes in driving behavior actually be detected.
2. Individual lever positions blink in Selector Lever Transmission Range Display Y5. This informs the driver that this gear can presently not be selected. An example: Reverse, lever in R and vehicle dives backward. If D is engaged in this situation, the letter D blinks in Selector Lever Transmission Range Display Y5. In this case, the control module prevents 1st gear from being engaged to avoid damaging the transmission. The gear is only engaged when vehicle is stopped. If you want to test this, do so carefully!
3. The Selector Lever Transmission Range Display Y5 is completely lit up and blinks. The selector lever position is indicated. An example of this: Transmission oil temperature is too high. Reasons can be, among other things: Towing trailer with too large of a load, auxiliary installations on front of vehicle, lack of cooling air.
4. Selector lever position cannot be recognized, Selector Lever Transmission Range Display Y5 blinks, changes in driving and shift behavior can be clearly detected, reverse not possible. There is a serious malfunction, a sub-gearbox is switched off, transmission repair is necessary.

Special notes about Fault Finding

Selector lever position display - no "R"
Simultaneous lighting of all segments of Transmission Range (TR) selector lever display indicates transmission in emergency running mode. The vehicle does not drive in reverse.

Tip function inoperable - no normal gear selection





Check lock washers on selector lever cable mounting bracket at top of transmission. Washer - B - especially must never be used twice.
This washer can be lost due to a loss of residual stress - arrow - points to cable adjustment screw.

Drive faulty - insufficient oil suspected
Only add oil if you have definitely seen: oil is leaking. Under any other circumstances it is just a needless expense that doesn't help.

No faults are stored
Experience shows that often a fault that is attributed to the transmission was caused by other components or units.
It has occurred that poor shifting behavior was a result of insufficient engine air supply.

Do not make mistakes like this.

If such faults are to be eliminated, you can work sensibly with the VW tester.

Faults are stored
First inform yourself of what the faults stored indicate. The VW tester offers the Guided Fault Finding possibility. You can find many causes of faults when the Guided Fault Finding is used correctly.

Transmission-external faults are stored
If, for example, the fault: "ABS signal missing" is stored in the transmission and perhaps another control module also says: "ABS signal missing", you should not continue to suspect the transmission control module is faulty.

The entry simply means: The transmission (and possibly other control modules) is waiting for a signal via the BUS but is not receiving it. In this case, the ABS control module has a problem. Under no circumstances should you remove the Direct Shift Gearbox (DSG) Mechatronic J743 without stopping to think. In this example, the fault points to problems with the ABS.