VCD re-occuring fault with no issues experienced..

[thegoal007]

I like to run a VCD check every so often, we are talking monthly, sometimes 3 months and every time this error pops up and i keep clearing it and it does go away. Even after a bit of a drive and recheck i dont see it, BUT on my next check a month or 2 later it posp back up. I notice no issues with the car, idles perfectly, no fluctuation on revs, fuel consumption is good, i can put my foot down and the power is delivered smoothly through the the rev range (no sudden bursts of turbo power). I have had additional occasional faults in the past (that were real!) that did require attentiion such as misfires on certain cylinders and they were resolved, but this specific error always pops up. The car has always passed the MOT for emissions for as long as I have had the car (which is 20 years!)

17863 = Exhaust Gas Temp Sensor 1 (G235): Implausible Signal
P1455 - 35 -10 - - Intermittent.

Obvosuly its not a serious issue, but just wondering whether others see this often?
Plus I gather replacing that EGT sensor it is a bit of a tight job, like a guess most things are in the tghtly packed engine.

 

[MPH]

I like to run a VCD check every so often, we are talking monthly, sometimes 3 months and every time this error pops up and i keep clearing it and it does go away. Even after a bit of a drive and recheck i dont see it, BUT on my next check a month or 2 later it posp back up. I notice no issues with the car, idles perfectly, no fluctuation on revs, fuel consumption is good, i can put my foot down and the power is delivered smoothly through the the rev range (no sudden bursts of turbo power). I have had additional occasional faults in the past (that were real!) that did require attentiion such as misfires on certain cylinders and they were resolved, but this specific error always pops up. The car has always passed the MOT for emissions for as long as I have had the car (which is 20 years!)

17863 = Exhaust Gas Temp Sensor 1 (G235): Implausible Signal
P1455 - 35 -10 - - Intermittent.

Obvosuly its not a serious issue, but just wondering whether others see this often?
Plus I gather replacing that EGT sensor it is a bit of a tight job, like a guess most things are in the tghtly packed engine.

Sounds like a loose connection, possibly being a fuse, not seen it personally, but there are a few threads on the TT forum if you Google 17863 = exhaust gas temp sensor 1 (g235): implausible signal

 

[thegoal007]

Sounds like a loose connection, possibly being a fuse, not seen it personally, but there are a few threads on the TT forum if you Google 17863 = exhaust gas temp sensor 1 (g235): implausible signal

thanks or i could simply continue to live with it until something happens.
Its been like that for years! I would have thought something would have happenned by now after so many years of it popping up

 

[superkarl]

The electrical connection is bolted to the underside of the inlet manifold, so surprisingly easy to check

 

[<tuffty/>]

Usually a sign that the sensor is on its way out... the electronics are potted into a plastic box fitted under the inlet manifold where its subject to heat and vibration... earlier electronics were potted in a jelly like compound and tended to allow components to break loose of soldered joints... later ones seem to be potted in a more solid compound...

Sadly an obsolete part these days like most of our parts (thanks VAG) so second hand is the only option...

One thing to be aware of is that when the EGT sensor goes into fault mode and is not getting a reliable or readable signal its default fuelling strategy is to literally p*ss fuel in at lambda 0.75 which not only increase MPG but will bore wash the cylinders and fuel will end up mixed in with the oil excessively... never a good thing

<tuffty/>

 

[thegoal007]

OK, understood. I see one guy on ebay selling second hand although based on what you say I guess most second hand ones are probably near to death too!?..Unless they were replaced since new. Mine is definetely the original one on the car as I have the previous owners full audi history with receipts and I have never touched it in the 20 years I have owned it.
There are a few Chinese ones being sold on ebay anything between £140 to £180. I've checked on all the usual part web sites and there's nowt!
So what would happen if this went in to a dealer for repair - would they simply say there is nothing they can do?
Oh I should also mention the oil and filter is changed every year regardless of mileage (except last year when i only did 70 miles!!) and the oil is alwasys very clean and no sign of petrol. Always passes the MOT (99% of time) and the mpg - i think - is vey good,

 

[<tuffty/>]

Its a difficult one tbh dude... its a lottery if you get a good second hand one these days and the only 'alternatives' I have seen were designed for S4/RS4 versions and they are subtly different in the electronics I believe

Sadly its going to be a problem going forward as our cars get older and VAG have mostly obsoleted the parts like the EGT sensor and Haldex controller both of which seem to have a finite lifespan and yet are key parts for our cars to operate correctly..

If its not giving you an obvious issue then you might be lucky especially if its intermittent but I am unsure of how it deals with an intermittent fault state over time... I think as long as the ECU gets a viable signal then its fine and will follow proper fuelling strategies but the minute it gets a bad signal it will go into a fault state until it sees a viable one again... but even then not sure if it keeps it at the fault sate until you cycle the ignition...

Our ECU's don't have a fault counter or time stamp setup like the later stuff sadly so makes it tricky to make an informed diagnosis outside of constant logging or monitoring...

Something like ColorMFA or equivalent OBD displays might help if you can get them to read the EGT sensor (not all the generic ones can) or maybe even AFR as overly rich on cruise would be a clue

<tuffty/>