temperature sensor/ECU? issue, looking for advice on what to do next

[valdamere]

Hey guys hopefully someone can help me out, I've got a 2007 9n3 polo GTI with a tune from MCTA, the car is running fine but for several months now I've been getting an engine fault for the engine temp sensor, the sensor has been replaced and fault cleared multiple times and has just been checked to see if the sensor is working/if the wiring is ok which it seems to be.

It's just come back from the mechanics again and he's basically said I've got no idea what's wrong, (didn't even charge me to check it all which was nice) and that hes having trouble even connecting the PC to the ECU at this point.

At this point I'm assuming the ECU is done, but I was hoping someone here could give me some advice on where to go from here, if there's a good auto electrician in Brisbane to go to that isn't gonna bankrupt me, or if I should just chuck in a stock ecu if I can find one. It's been months of trying to get this sorted now and I'm at the end of my rope 😅 thanks for any help

[h100vw]

What does the code say on VCDS? Is it Coolant temp sensor implausible signal?

If so and you've done the temp sensor multiple times.

Replace the thermostat and owe me a drink

Let me know

[valdamere]

The code is intermittent temperature sensor for sensor 1, which is the one that was replaced and had all the wiring etc checked, everything else is good at this point.

I've got a cheap replacement ECU coming from someone I know that I'm gonna try out and see what happens so I can narrow down if the ECU is the issue since there was an issue even connecting to it, so I'll see if the same fault comes back up.

[h100vw]

The code is intermittent temperature sensor for sensor 1, which is the one that was replaced and had all the wiring etc checked, everything else is good at this point.

I've got a cheap replacement ECU coming from someone I know that I'm gonna try out and see what happens so I can narrow down if the ECU is the issue since there was an issue even connecting to it, so I'll see if the same fault comes back up.

Keen to know what you find

[valdamere]

Well it looks like the issue is probably fixed, and what a silly reason it was. Had the battery be completely dead when I went to go to work Friday, I thought the alternator might have gone because the battery had 19 written on top (the year I assumed it was changed) and tested fine on the multimeter.

Jumped the car and after running it for a while tuned it off and tried cranking it, was super sluggish at first and after about 10-15 tried it managed to start. At that point I tested it again with the multimeter and sure enough it was WAY low. I go to put the new battery in and what do I find? SOMEONE PUT 19/6/14 ON THE BATTERY BUT THE ONLY PART SHOWING WAS THE 19. It's was an 8 year old battery, apparently me and and multiple mechanics missed it and after changing it, the check engine lights gone and looks like everything is working correctly. I just need to clear the error code from when the sensor was tested, I'm betting the ECU is gonna have no issue being connected to, looks like it might be all good now.

If anyone in Brisbane has a cable and would be kind enough to clear things for me let me know, I'll grab a 6 pack as thanks, I also now have a flashed ECU coming in the mail that I don't need if anyone is looking for one cheap 😂