Had the motor pulled to install an AMS Alpha 9 kit. Put it all back together had the car dyno tuned no issues. Few days later temp gauges drops to far left as in not taking a reading, red light starts to flash and the message " temperature indicator failure". After a little bit of driving it all of a sudden starts working as nothing happens.

Problem now persists and it now is 70 percent not working while I am driving and 30 percent working. Just jumps back and forth with no rhyme or reason. Could be idling in the driveway and it goes from working to not working or vice versa.

Swapped temp sensor initially as well as solenoid in tranny ( it's a tip car) did nothing. Swapped the solenoid as the error message we were getting during the scan was in the tranny for some reason.

Thought maybe there was air trapped in the system but that's just doesn't make sense as I have put 1000 miles on the car, have driven with relief valve open on coolant tank to let any air out and the problem still persists. One time I went sideways around a corner and it started to work just from that motion.

Also, however the car shuts off is how it will come back if you restart it. Ie if you shut the car off with the gauge not working and the red lighter flashing that's how it will start next time or vice versa.

What's also interesting is that when you scan the car while the error message is on the scanner is receiving the coolant temp from the car.

Any ideas? Haven't put a ton of effort into figuring it out as I have been travelling but it's time to source the issue.

 

broken wire? bad connection? maybe something got pinched?

 

Checked all the connections, car will do it just sitting there idling in driveway not moving.

 

how is your battery? I have heard of some electrical gremlins with a weaker battery.

 

Battery is brand new after the Alpha 9 install. Thinking of maybe reflushing the coolant. Electrical connections are all good. Going to check for continuity on the wires that send signal. But doubt it's that as the diagnostic computer shows the temperature when scanning car.

 

I had an oil pressure gauge doing the same thing and it turn out to be the sending unit but you send you have already swapped that. I can't believe two would be bad but you never know.

 

Just replace the sensor, I had the same problem on my 2010 GTS Cayenne and it was the $20 temperature sensor that was not working right

 

I've done that already, maybe worth swapping it out again.

 

Did you ever figure out the cause and the fix

 

I'd like to know also because my car is doing the exact same thing. Thanks for saving me the trouble of changing the sensor and checking for air in the system.

 

It was the changeover valve and heater valve of the transmission cooling system.

 

Is that part unique to a Tiptronic car? That is what the OP said he had.