Newbie with a TQS

[arch-stanton]

Hi all, firstly I'm new to the forum so hello..
I've got an A4 1999 TQS, which is running cool, as in cold.... I've had it on VAGCOM and it showed CTS intermittent fault, I've changed the CTS, but still got the same problem.. I've had a look around this site, there's some great info on here and I found how to check the CTS using Ch49 on the climate control.. this was showing 60 degrees max on a run, then steadily climbed on idle up to 90 degrees... so, this leads me to change the Tstat (which I'm doing today) I'm pretty confident this will solve the problem... I realise if I'd used ch49 first, then I would've been able to narrow it down to the Tstat straightaway..
However, the VAGCOM data showed the CTS as faulty...hence me changing that first.. Anyone know why it would do this?
Am I heading in the right way with this?

 

[aragorn]

If you'd read the code carefully, you'd have noticed it didnt say it was faulty, it would have said "implausible value, intermittant".

The reason for this is with a broken stat, the temp will climb and fall depending on the cars speed. The ECU knows the temp should climb to 90 and stay there (within 10c or so), so when it sees it moving all over the shop (or simply never reaching 90) it flags a fault because it can see something isnt right with the temperature. It obviously has no way of knowing if the sensor is faulty or the actual temp is wonky, so it specifies that the value is implausible.

If you unplugged it, you'd have got a code like "open circuit" or similar.

Fault codes can be a really useful help, but they need to be taken with a pinch of salt, and you need to think about how the ECU thinks and processes its data before diving in and changing parts.

 

[arch-stanton]

aragorn Thanks for the info.. tbh I never noticed "implausible value, intermittant"... not such a costly error mind.. this time.. !
I'm new to the VAGCOM data reading, so if you'll allow me to use that as an excuse?!

 

[ScottyP45]

logging is the best function in vagcom mate, and Aragorn has a unique clarity of thought on technical stuff so don't feel bad you missed that one

If you run a log, you capture the entire behaviour over time of a particular sensor or value or function. Much better than a snapshot code, and several things can be captured (2 at a time are best) then overlaid in a graph to see what other stuff is going wrong at the same time or reacting to a wrong value - can often point out the true culprit.

I'm still trying to get my blue ebay vag lead to work on my vista laptop, its seen by the software but vagcom cant see the car, my autel vag405 scanner works perfectly so its not the car but its ****** annoying. Its the dumb usb > serial one but other folk have got them working fine with 409 or 311 vagcom.


I saw a post somewhere on a US forum about an additional driver but cant find it anymore.

 

[arch-stanton]

evilscotsman
I'm no pc guru by any stretch.. my mate plugged his Vagcom into my car to see if we could find the problem.. it just shows though, that it's ok throwing up codes, they need to be interpreted correctly!
Anyway, car is done.. running great again, dial sits at 90.
The bolts holding the plastic housing took the longest to get at, ended up undoing the mount in front of it, just to give easier access.. no problems after that

 

[jcb]

I'm still trying to get my blue ebay vag lead to work on my vista laptop.

I have found your problem!!
vista is a virus and should be purged from any computer

 

[NineNails]

^^^ what he said lol