Triptronic problem

aussiehussey · 08-05-2008, 01:59 PM

Can anyone help !
i have a 1990 C2 with triptronic. the car runs great but occassionally the gearbox light on the dash comes on and the gear box clunks when put into gear. if i disconnect the cable to the transmission control module under the drivers seat, and replug in, the light goes off and the car runs perfect with triptronic. If the light on the dash is off when the car is started the car runs perfect but when light is on I have to reset it as per my explanation above. we replaced the TCM with a new one but it still does the same thing. any clues ?

thanks

jm993rs · 08-05-2008, 11:27 PM

I have just the same problem in my car. the light of triptonic gearbox always comes on , and the gearbox input de gear of emergenci. when I stop the car and make run another one the ligth is off and the car runs perfect.

I asked in differents workshop and they would change the gearbox, but is not the gearbox, is a little problem with one sensor or electric part of the car, make one error to the control unit, and the control unit insert the emergenci gear.

but when the ligt not goes off the car have a problem.

aussiehussey · 08-06-2008, 07:45 AM

You sound like you have the same problem as me. Do you know if there is another electrical part that could be changed to rectify the problem ? I have changed the Transmission Control Module and its the same thing. When the light is off it drives perfectly well, when on its in limp mode !!

i hope you can find a solution. I will continue to search for a cure.
thanks

Quote:

Originally Posted by jm993rs

I have just the same problem in my car. the light of triptonic gearbox always comes on , and the gearbox input de gear of emergenci. when I stop the car and make run another one the ligth is off and the car runs perfect.

I asked in differents workshop and they would change the gearbox, but is not the gearbox, is a little problem with one sensor or electric part of the car, make one error to the control unit, and the control unit insert the emergenci gear.

but when the ligt not goes off the car have a problem.

ischmitz · ischmitz's Garage

I suggest scanning the error codes with a Bosch "Hammer" or Porsche System Tester. Most indenendent Porsche shops have these tools. The error code will tell you what caused the control module to switch to emergency mode.

aussiehussey · 08-07-2008, 06:20 AM

Thank you for your reply.
my problem is I live in the Bahamas !!! nobody has a scanning tool - do you know where I could buy one from ?

ischmitz · ischmitz's Garage

Well, a Hammer is around 800$ - 1200$ depending where you buy. The PST2 can be had for 2000$ for a clone while real ones go for up to 4000$. Not sure if that is an ecconomic solution for just one service event.

There is a company called www.Durametric.com that makes a cheaper aftermarket scan solution. I think it is around 300$ and you need a laptop or computer with USB. From what I hear it seems to work well for most stuff. Maybe that is a good alternative.

BTW: I'd be happy to come down there with my Hammer or PST2 and do the scanning

An airline ticket is probably a lot cheaper than buying a Porsche scanner. (just day-dreaming)

Cheers,
Ingo

aussiehussey · 08-17-2008, 07:15 AM

thanks for your advice and offer to fly down to help (-:
i went to durametric and purchased the scanner/software. it showed that I have an error - #24 - change of ignition timing !! what do you think that means ?

I also found errors under the motronic -

O2 sensor
knock sensor 2

i have ordered these parts from pelican parts. any idea how to install - I have the Bentley book and read many of the forums but still a little lost. any help would be appreciated.
cheers

ischmitz · ischmitz's Garage

I don't know the meanings of any error codes of the Tiptronic computer. Are you sure the #24 comes from the Tiptronic and not from the DME. What is the explanation from the Durametric for that error?

What I do know is that when the tiptronic computer initiates a shifts it sends a signal to the DME to momentarily retard the timimg. This is to reduce the torque flowing through the gear box for easier shifting. I could see that the DME doesn't properly process that signal with the knock sensor being bad and timing already being retarded. However, to my knowledge there is no way for the tiptronic module to "notice" that the shift signal wasn't properly acted on by the DME. So I don't know why the tiptronic would throw up a fault code.

The Motronic uses two knock sensors (one on each bank of cylinders) to check for knocking. There is an aluminum bridge mounted to the cylinders and the knock sensor sits in the middle of that bridge. It acts like a microphone. Once knocking is detected the ignition for that cylinder is retarted to prevent further knocking. This is a feedback loop.

The knock sensor is a piezo-electic sensor that generates a small voltage spike when it gets deformed. There is a special screw for mounting the sensor and you need to follow the mounting specifications (torque) precisely to make sure they work. They are located under the black plastic engine shroud. You might get to them when you remove the alternator/fan. Not sure if the intake and shroud can stay on but I think it should be feasable with it still in place.

If knock sensors #2 is not working the DME will issue fault code #1_32 (knock signal not plausible) and the ignition will be retarded by 6 degrees to prevent damage. You will notice a loss of power, too.

The O2-sensor is easy. If the sensor voltage "seen" by the DME is less than 0.1 Volts or more than 1.0 Volts and error code 1_24 is generated and the system will not use the O2-sensor driven closed loop system. Replace the O2-senor. These sensors age with time. It could also be a bad connector with faulty contacts. If you unplug and re-plug it a couple of times it might solve the problem. The connector is located in the engine bay on the left side. It is a black round thing towards the back. You might have to do some searching. Try the same for the knock sensor. I don't know which one is which but the connectors are green. One is on top of the intake and the other is on the bracket on the left side of the engine where the vacuum and fuel lines go. They are three-pin if I remember correctly. Unplugging and re-plugging cleans the contacts.

Hope that helps,
Ingo

ischmitz · ischmitz's Garage

Here is one knock sensor connector. I would guess it is #2 but I don't know for sure. Just unplug it, start the engine and see if you get error 1_31 (knock sensor #1) on top of 1_32 (knock sensor #2). That is the easiest way to find out. If yes it was #1, if no it was #2.

And here is the other one shown with the engine out of the car. This one will be a little harder to get to.

And here you can see the knock sensor mounted to the bridge on the shortblock (before the rebuilt):

and after the rebuilt.....

Note the orientation of the wires. Only the black part comes out. Do not remove the brides. The workshop manual recomends to replace the microencapsulated Hexagon mounting screw when replacing the knock sensor since the correct torque of 20Nm is critical for proper operation. The part number is 999 217 082 02. I don't know how critical that is. Do not use a washer.
Ingo