could anyone with vcds and the same car, please log group 102 and see what your temp is at, mine is at 551 all the time?

 

Is there an actual fault code your are tracing, or are you just looking around and seeing numbers you don't understand?

 

The car is going into limp, no mil or faults logged. So trying to trace the issue, key off and key on takes the car out of limp but it goes back into limp pretty quickly.

 

Does anyone know which sensor measures that temp? I have unplugged the egt sensor which logs a fault straight away but that temp doesn't change.

 

It sounds like you have VCDS, but if you don't, you should get one since basic/generic scantools can't communicate with this car due to the VAG (Volkswagen Auto Group) proprietary software. A standard OBD2 scanner is not going to make a dent in it.

As to the 'temp' reading sticking, that's a classic symptom of a bad sensor, or it being in a default loop due to bad sensor. I had that happen when my EGR Cooler went out...temps spiked and cooked the downstream exhaust temp sensor, which threw the system into a default loop, and the car reduced boost, etc., to reduce the temps reported...limp-mode, basically. Be sure to check your coolant reservoir level.

 

I do have vcds, trying to figure out which sensor would be related to the pre cat temp. Looks like my car doesnt have a dpf well there are no pressure sensors or temp sensors on the dpf so the only other 2 sensors I can see are the actual egt sensor on the turbo ie pre turbo and then the lambda probe which is pre cat.

 

As referenced, it is not uncommon to 'cook' a downstream sensor, post-EGR Cooler, if there is a problem with the EGR Cooler itself. Often times with this car, one bad sensor will create a 'cascading' effect or throw the car into a default loop to protect itself. In short, it could be a Nox sensor that's actually bad and throwing the car into a default loop. All sorts of strange things can, and do happen when you lose an emissions sensor on this car. The temperature 'squirrel' you've gotten locked onto is most likely symptomatic of the actual issue, and not the actual root-cause issue.

Be sure to check your coolant reservoir level to see if it's low or nonexistent...that's a sign of an EGR Cooler leak, which causes downstream sensor failures, feedback loop issues, limp-mode, etc. While that may not be your base issue, it's certainly easy to check for. The TDI models also get very thick carbon/soot deposit build-up in the intake tracts/EGR system, etc., over time related to being a direct-injection engine, which narrows the air passages down to the point where you'll wonder how it still runs at all. Had the EGR Cooler replaced at 108k miles on our 2010 TDI, and it was coked-up so severely inside that Audi actually cleaned it out gratis prior to reassembly; didn't even notify me about it...a very rare thing in the USA where they prefer just to sell you new intakes rather than de-coke the old ones. Liqui Moly has introduced a TDI intake cleaner spray (introduced via vacuum line) to address the soot/carbon build-up issues w/o having to disassemble the car.

I've had two different emissions sensors go out; one threw the adblue monitoring system into panic mode, and threatened to disable the car, although the adblue tanks were full and functional. The other related to the EGR Cooler failure, which allows too much exhaust heat to pass through and damages the downstream sensor bits; it put the car into a protective 'loop' and cut power output...all seemingly unrelated to emissions sensors. Look for what can be creating the data point, not just at the data point itself.

Good luck!

 

thanks, in my experience usually all vag cars will log some sort of fault in this regard and this time there is nothing being logged which is making troubleshooting quite difficult.

 

so I have gone through all the temps, engine, oil, intake, egt and fuel, the only one that I am not sure about is my fuel temp which after a short 10 minute drive gets to about 80C, can anyone else check there fuel temp via vcds to confirm if this is normal?

 

so it was my fuel temp sensor, looks like it limits torque anything above 70C