zf-as-tronic transmission problem.

Hi dear friends,


I am new here and my English is no so good, so I hope you'll have nerves to read and hopefully give some kind of help.


I am trying to fix an problem with ZF-AS-TRONIC transmission electronic module.
When engine is started transmission won't switch to neutral for some time till engine and transmission is heated up.
We have found that if we heat top of the actuator module with heat gun, it speed up this process significantly.


According to the operators manual, all this may happens if ambient temperature is below -20 deg. Celsius.

But the problem is that it happens in relatively hot day every time engine is cold started. As I have found there is oil temp. sensor in transmission actuator and it is connected to the transmission controller electronic board, but is seems like it is ok. I suspect there is other on-board ambient temp. sensor that may be faulty.
I've tried to locate this sensor on the printed board but without success.


Found this picture here on forum.




This is same board as mine.


Can someone help about this problem? I see there are many experts so I hope someone may help me to solve this.
Is there some on-board temperature sensor that can be source of this like problem?

I will be glad to get any kind of help.
Thanks and best regards...

 

Thanks for comments,


At this moment transmission is dismounted so I can not do tests but I'll be able to do it soon.


If I catch you, I must restart TCU whilst engine is running to fool TCU and skip clutch test, right?


I work on IVECO EUROSTAR truck and have not any kind of software at the moment. Some time ago guy who did diagnostic found there is temp sensor in TCU reading -10 degC whilst ambient temp is above zero. That is why I suspect there must be some onboard temp sensor but I have not more details about what he have found.


Weird thing is that now at +15 degC it takes about one hour to worm up and to switch to neutral. If it is cold it takes longer.


The fact they did not say to me before is that there is error displayed on transmission panel display, about 10 minutes after engine start.
Spanner is displayed at first and error code 32 can be read.
After additional 30 seconds or so, STOP and spanner are displayed together and now error 154 can be read following after error 32. Now if you restart engine it starts again from the begining.
Error will disappear when engine rises temperature of transmission box. As I have said it takes long time.


I do not know what error 32 means. Can't find that error on the list in manual.


But, if top cover of tranny actuator where electronic PCB is located is heated with hot air gun, transmission switch to neutral possition in just 3 minutes without any error displayed.


It is hard to believe that anything else but electronic board can be heated in just 3 min. There must be cold solder junction or faulty temperature sensor in TCU but that is just my opinion and I may be wrong.

Like to hear from you guys.

 

Repairing solder joints is not a problem but signal trace on this board is a hard task. Do you or someone else have circuit diagram of this board?
There is one temp sensor rinsed in oil and I have located it, but is it possible there is on board sensor?
I have no tech info about the electronic board. Is there some tech manual that may be helpful?
I can do a reflow of whole board but it may produce other faults and than I am in trouble.

Many many thanks for your help friend.

If you have any additional comment please...

 

Yes I know diagram is secret information but if I ask, it will not kill me .
Reverse engineering is hard to do on this board if you do not like to destroy it.


I will inform you about the progress if there is any.


Regards.

 

Some documentation for reading can be found here.

https://www.scribd.com/doc/137329516/ZF-as-Tronic-Description

Regards.