Blinking light between Drive and 4th gear on a 986 Tiptronic

[ClaudeJS]

Maybe useful for all:
With an OBD code reader, I found the code P0740 "Torque Converter Clutch Circuit/Open"
I erased the fault and problem is gone, solved : no more light blinking, everything works perfectly!

So simple as that!

Lesson learnt: OBD code reader is mandaotry!

Thanks to all for the support,

JC

[Dale_K]

Simply erasing the code may not have corrected the underlying problem. My car is in the shop right now and one of the items is the 0740 code. I am hopeful that a Tiptronic service with fluid and filter replacement will have a positive effect on my car but I really won't know until I drive the car for a while. I hope your car doesn't need any additional work but simply clearing the code might not be enough. My mechanic thinks the Tip fluid gets contaminated with diff fluid and then the torque converter clutch slips. Personally I doubt it. I told him to go ahead and take a fluid sample for lab analysis but I don't know if they can really detect cross contamination or not.

I'm supposed to get my car back early this week and I'll post an update. It would be good news if the Tip service decisively fixed it because that's fairly easy and cheap. Stay tuned, as George Bush the elder used to say.

[bcorcoran]

Hi, I've just joined this forum - grate source of info.

My 2001 Boxster S tiptronic has similar symptoms: some gearbox slip & alternating fault lamp indications.

I'll have to look up the fault code provided from my dealer but their suggested fix was a gearbox overhaul as they claimed the torque converter was worn and residue evident in pan. I took the car to a transmission specialist who had trouble identifying any problems but we agreed to an oil & filter change and some further fault diagnosis. The specialist indicated no one had removed the pan previously and no evidence of residue from torque converter.

The filter & oil change improved the situation for low speed driving but at higher speeds I still get fault lamps, but not always and no slip, no noises, no fluid loss, in fact no change in performance ie can manual shift as normal.

From this forum & others it seems possible causes include wheel speed sensors, transmission plug/sensor or transmission control unit on boot (trunk) wall.

I hope others out there can sort this one!