Hi, I am new to this site and have found it very useful by sorting out on fault already. I have a 2001 Octavia Tdi and the outside temperature display is showing -34 degrees C, this varies a lot of the time and on rare occasions it shows the correct temperature, have changed the temperature sensor G17 behind the nearside front grill, and checked it's earth connection which was OK, still the same. Has anyone had this fault and knows what is causing it, otherwise does anyone know if this temperature is sent to the engime management so it knows what the ambient temperature is to fuel the engine correctly.

Thanks in advance for any help that you can give.

I think that temperature is used to control how long the glowplugs come on for, and also to enable/disable aircon. iirc aircon does not work under 5 deg C (or is it 3?), even though the display will suggest it is, nocold air gets pumped though, so that might be worth checking....

I would imagine vagcom can access the temperature feed, so that help determine if the sensor/cabling is screwy, or if it is the climatronic display which is playing up.

Which figure is wrong, the left hand one on the Climatronic or the one on the MFD under the rev counter? IIRC the sensor on the bumper only provides the figure for the MFD, there is another sensor somewhere near the wipers/scuttle panel that does the figure for the Climatronic

Thanks guys, the temperature display I am refering to is the one on the multifunction display on the dashboard, not the one on the climate control that reads correctly.

Glow plugs are controlled via the coolant temp sensor. Not sure if temperature is used for fuelling, it might be done solely from the MAF and MAP sensors but I might be wrong.

May be a faulty MFD display then, if you have already checked and replaced the sensor in the bumper. I would expect your fuel economy to have taken a massive nosedive if the fueling is based on a reading of -34 degrees from the temp sensor

Thanks for the posts on this problem, fuel consumption seems to be lower than usual by about 5mpg, but might be the very cold weather, trying a trip tomorrow on motorway which I have done a lot of times before, so know what to expect mpg wise, will post what I find out after trip. If this fault does not affect the engine and economy if there is no simple solution might ignore it, as spend hour trying to sort it out.

Did the trip yesterday and seems to be 5 or 6 mpg down I what I normally get on that trip, anybody help please.

Edited 1 March, 200917 yr by GSM1954
Update information

5mpg down compared with what sort of time of year? I'd expect that sort of hit compared with, say, August, between the cooler ambiant and Winter diesel. Of course, if it's compared with a trip done, say, early February before the outside temp started playing up it's not that.

Trundlenut's right on though about the glowplugs and cold start being controlled by the water temperature; after all, even at -20C, if you get the engine hot, then stall and re-start it will still be hot!

Ok, will forget lower mpg, maybe due to cold weather, but that still does not solve the dashboard temperature display showing minus 40 degrees C. All other displays are operating normally, any ideas on this one please.

just to be clear is the climatronic showing the same daft temp as on the dash?

No the Climatronic is showing the correct outside temperature, it is the Instrument panel multifunction display that is showing the wrong temperature, though all it's other functions are working OK, does that help?

sounds like a problem with the instrument panel then. The question is does the dash get the raw signal or is it processed by the ECU beforehand. If it is the raw signal could there be a wiring problem in the wires going to the dash which screws up the signal. Could be a bugger to chase down all the wiring to find the problem.

I used to have an astra which would vary between +60 and -60 on the temp display, it was rather funny really.

If the problem is the dash then you probably just want to live with it as changing the dash pod seems to be a serious pain in the posterior.

Have looked further into this fault and looks like there is extra resistance between the sensor and the input connection of the instrument panel.

Can anyone tell me if there are any plugs and socket connections between the sensor and instrument panel?, and if yes where are they?