[chuaed]

Guys,


Figured I should start a new thread for this given the issue that i have with the Tiptronic going into limp mode (intermittently) is turning into a nightmare!


So initially the specialist figured it was a low voltage issue triggered by the high resistance (low voltage) in one of the cables connecting to the battery terminal. Had it replaced but still did not solve the issue. Now they are saying it is the impulse sender (94460611500) that needs to be replaced. This was a part that i had replaced about 3 months ago with a Bosch unit. On doing further research on the autoatlanta website, it appears there are two senders required. One that measures crankshaft position and the other measures speed. Any idea if this is the case and is the part number identical for both?



Thanks

Ed

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[unknown4u]

The tiptronic also get a signal from the dme. So if that signal is poor you will have a similar symptom. If you turn of thd key and put it on again it is solved.

But describe when it appears is it random or can you repeat the circumstances when the light will come up?

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[chuaed]

The tip light comes on usually 3-5mins into driving and when this happens it goes into limp mode with restricted driving. Turn the ignition off and restart the car, the light will not appear but doesnt take long for it to then come back on again while driving.

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[unknown4u]

Have you tried not to drive in D but in third gear. Wil it happen than either.

Is the ground good for the module tipcomputer in the rear backtrunk? No bad connection.

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[chuaed]

I dont have access to the car now - awaiting a new impulse sender unit at the specialist workshop. Hopefully a new sender unit will solve the problem. Will update again.

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[chuaed]

Update from the Porsche specialist this morning:

 

1.  Impulse sender on the car was replaced, did not solve the Tiptronic limp mode / stalling issue.

 

2.  Temperature gauge needle continues to fluctuate randomly (had this issue as mentioned previously).

 

Then I had another update in the evening:

 

1. They had the vehicle re-checked and noticed the ground strap cable connecting to the negative battery terminal was loose.  So they fixed it and miraculously solved both the limp mode and temperature gauge issues!

 

 

So the specialist told me that it was the ground strap that was causing the limp mode / stalling of the engine, and the new impulse sender that fixed the temperature gauge issue.   And they insisted a new impulse sender was needed to fix the gauge (FYI - I had the impulse sender replaced about 3 months ago).   This didn't quite make sense to me as after they replaced the impulse sender both problems still existed!

 

Can someone please advise if a defective impulse sender would or may affect the temperature gauge reading?  From what i know the answer is probably no.  Unless i'm wrong...

 

 

Thanks

Ed

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[ds968]

Very interesting to learn that a simple battery cable connection can impact the transmission's m.o. in a car with rather "old" technology ; in my Mercedes which is 10 years younger than the 968 a minor battery / alternator voltage drop ( 0.5 V ) will put the transmission into Low gear and that mode cannot be overridden until you fix the problem.  The same happens ( Low gear )  if the coolant system temps are a certain number of degrees below or above what the computer deems to be allowable operating parameters.  But I did not think those finicky computer things would be also the case in a 968..                    

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[Rap]

This is the first post I've seen in several days. Anyone else experiencing this?

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[ds968]

yes, i was wondering why it's so "slow".. the vacation season has not quite started yet.. :glare:

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[Waylander]

_{one of the first jobs on these cars appears to be go through all the earths, it seems to cause all sorts of strange problems.}

 

_{look at the wiring diagrams and go hunting for all the earth posts and clean them. well worth the effort.}

 

_{and I also think the impulse sender had nothing to do with the temp gauge}

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[ds968]

What the heck is an impulse sender ? First I've ever heard that term used here...or anywhere. Is it the same as a hall sender ?

I read in the original post what the two senders measure , but still...is it it something entirely different than the hall sender ? Or is that called a hall sensor ? I'm totally confused now with senders and sensors ..

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[chuaed]

Hall sensor sends a signal to the control unit to cause the coils to spark. Impulse sensor measure crakshaft position and speed. Two different things. I suppose sender and sensor can be used interchangeably!

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[ds968]

Ah, ok.

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[Waylander]

Hall effect sensors / senders are used for all sorts of things, ABS, Speedo, Gearbox, they are just in different casings.

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[ds968]

So what are the specific symptoms of our cars when they go into " limp mode " ? Is it a RPM restriction , or certain gears restriction, or what ..?


p.s. and if you drop a Viagra pill in the gas tank will it temporarily resolve the LIMP mode ? Sorry, could not resist ..

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[Waylander]

no does not fix the limp mode but makes the suspension stiffer

 

if the engine hall sensor does not work, the ecu retards the ignition timing and then starts firing the injectors two at a time as it has no idea what firing sequence its in.

 

as for the gear box it must sense rotational speed of the clutches or something Auto boxes are not my forte

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[968Syncro]

Well, the finding of an electrical problem sounds familiar as a cause of the Tiptronic limp mode.  Limp mode happened to me once, during a jump start.   Can't recall the details of why the battery went dead, but we had to get a battery jump start (at the airport of course!).  Somehow when the car started, the trans went into limp mode.  Drove it home that way, because I didn't want to turn the car off, since the battery was hardly charged from the jump start.  So turning it off would have meant another jump.  When I started it the next day, the tip was normal and it has never happened again.  So both of these instances point to limp mode being set when the voltage is somehow too low.

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[unknown4u]

Limpmode means stuck in second gear and stumbling shift when you go from neutral to drive. But in 2nd you can drive fast enough to get a speeding ticket.

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[MCL968]

Where would the diagram be of all the ground locations? I can find some, but the dash ones and other hidden ones are unknown to me at the moment, and I would like to address them before summer driving time begins.

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[968Syncro]

The wiring diagram has the details.  I have the file "Wiringdiagram93.pdf" on file, can't remember where I got it, most likely it is stashed away here on the forum somewhere.  It has both a table with the list and a car "top view" showing the locations at the end of the document on pages 40-43.

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