996 auto transmission won't change to 5th

[steve996]

Howdy guys

New contributor to the forum and owner of a '99 996 Cab with 60K.

Recent problem is in automatic mode, at freeway speeds and 4000rpm, the auto transmission refuses to change to 4th or 5th. I have to go to tiptronic to make the change and there is no problem in that mode.

No fault codes are showing and the mechanic is suggesting that the control module for the transmission may be faulty and needs replacing.

Any experience with this that might point me in the right direction before an expensive module replacement? Thanks

Steve

[Loren]

When did you last change the ATF?

If not recently I would start with that.

[Izzy]

Steve, I am surprised no codes are showing. I would go to Autozone and borrow their reader and verify that.

The other thing that may be acting up is the speed sensing unit on the transmission. Specially if the fluid is old. You said it does shift on manual mode, so that is what got me thinking fluid or pressure regulator or transmission speed sensor in the hydraulic control unit.

[steve996]

Thanks for the prompt response Loren and Izzy.

The ATF was changed in January this year.

Can check codes again but can say that two separate checks with different readers have occurred.

Will go to our version of Autozone and check the codes again and report back. Thanks!

When did you last change the ATF?

If not recently I would start with that.

[Loren]

Hmm... did they use Porsche spec ATF?

[steve996]

I don't know Loren. They are Porsche service providers so I would hope so. I will ask them that when I see them again tomorrow. I take it from your comments that you were not convinced that it was the module then.

However, the good news from my last post was that they disconnected the battery overnight and now the transmission is going to 5th in Auto fine now, although the transmission appears to be 're-learning' itself and is not as fluid as it should be but is definitely cycling through all the gears. I am hoping that will avoid the need for a module replacement. Since I did not buy the car from new is the re-learning process normal??

Thanks again guys...love the forum and all the info.

Hmm... did they use Porsche spec ATF?

[Dante]

I don't know Loren. They are Porsche service providers so I would hope so. I will ask them that when I see them again tomorrow. I take it from your comments that you were not convinced that it was the module then.

However, the good news from my last post was that they disconnected the battery overnight and now the transmission is going to 5th in Auto fine now, although the transmission appears to be 're-learning' itself and is not as fluid as it should be but is definitely cycling through all the gears. I am hoping that will avoid the need for a module replacement. Since I did not buy the car from new is the re-learning process normal??

Thanks again guys...love the forum and all the info.

Hmm... did they use Porsche spec ATF?

Just to let you know - had a similar problem with my Boxster and it never threw a code. To give you a background, in Manual mode the tip would intermittently go out - roughly 1x per week. Dealership told me to try and bring it in to them when occurring. After several months, I finally got it to them when it was happening and nothing was showing up on their diag tools. No shorts, failures, etc. It had them baffled and they finally had to consult with Porsche Germany. Over the next week while they were waiting the answer - my water pump blew.

After having the car towed in to the dealership - I traded it in for a C2 Cab. So unfortunately I never did find out what the mystery problem was with my tip.

Anyways, good luck and hopefully you don't have any more problems.

[steve996]

Thanks Dante

So far so good...... Everything appears to be back to normal. I did confirm that no codes came up with a third reading and that Porsche spec ATF was used so it is a mystery why it happened.

At present, after disconnecting the battery, the auto transmission has remapped itself to a city traffic cycle with gear changes to 5th @ 2000RPM and around 60km/h. It may also be a product of the careful way I am driving at the moment as well. Any way lets hope it is not something more sinister and thanks for your interest. Mine is a c2 cab also..so lets hope you don't suffer the same circumstances :)

Steve

Just to let you know - had a similar problem with my Boxster and it never threw a code. To give you a background, in Manual mode the tip would intermittently go out - roughly 1x per week. Dealership told me to try and bring it in to them when occurring. After several months, I finally got it to them when it was happening and nothing was showing up on their diag tools. No shorts, failures, etc. It had them baffled and they finally had to consult with Porsche Germany. Over the next week while they were waiting the answer - my water pump blew.

After having the car towed in to the dealership - I traded it in for a C2 Cab. So unfortunately I never did find out what the mystery problem was with my tip.

Anyways, good luck and hopefully you don't have any more problems.