Sensor failure - Same one 3 times in 20 months!!

[DMitch16]

Hi All,

Scratching my head over this one!

I have a MIL on and VCDS reports that my G235 temperature sensor (post turbo, pre DPF) has failed yet again after 6 months perfect running.

The sensor that has gone is 03L 906 088 BS (this is the most recent VW part number) and this is the 3rd time in 20 months that it has failed but not until after 6 months each time. I would suspect a wiring fault but this does not tie in with 6 months good use as I would expect a wiring issue to affect it a lot earlier? I note that the newer version of the part does not have the older style mesh / foil heat protection - and yet it sits right under the turbo on the manifold body almost the hottest space you can get!

At £112.50 plus VAT it's an expensive item to replace every 6 months or so - does anyone have any ideas as to why it keeps failing almost like clockwork after 6 months? None of the other temperature or Lambda sensors are affected.

I now have the Exhaust Gas warning light and DPF saturation lights on (just today) which means it has not done a regen for a while (I do 80 miles a day at at least 50 to 70mph for over 30 minutes so would expect a forced regeneration to happen - the sensor failure is probably stopping the regens if it won't read the temp at the pre DPF end).

I also have a glow plug fault on cylinder 2 but have noticed a slightly more lumpy start over the past month most of which have been cold so it probably has gone after 110,000 miles. I'll change all 4 anyway - VW recommend changing every 60,000 - not sure many owners do until they actually fail.

Any help would be appreciated as everything else about the car is great (except the EPB!).

Many thanks
Mitch.

[martin1810]

Have you asked VW about free replacement under warranty?

[DMitch16]

Unfortunately the car is well over its warranty period now and although VW have completed all recall work such as injectors, wire looms and so forth they will only cover these items under a warranty and for a limited time only. I also have to tackle a sticky rear EPB motor which is throwing up another code now (have practically memorised your piece on these Martin) something which I am not looking forward to. I am led to believe that I won't be able to even force a regen without changing the sensor as it relies on a pre DPF temp of 700 degrees or more as read by the said sensor. It could be that the sensor is being overloaded to a point of premature death somehow but I'm not sure how to check this?

[Guest 2]

Any part purchased from VW will have a 2 years guarantee so if it fails within 2 years, take it back and get a free replacement.

[DMitch16]

Thanks A6_Chris, wasn't aware of this and still have the receipt as P.o.P. Will go to local dealer this week and see what they say. Many thanks.

[DSG4ME]

Thanks A6_Chris, wasn't aware of this and still have the receipt as P.o.P. Will go to local dealer this week and see what they say. Many thanks.

Take it in on the car so they can see it's failed, they may want to charge you a diag fee if they find it's not broken but if it is that will get waived

[-M-]

Check to make sure you also have the most up to date software on the engine ecu.

[DMitch16]

I have an update!!!!
I took the car in to VW as suggested by DSG4ME and they performed the diag and full test plan on the failed sensor (which was the ONLY issue - made sure of that with VCDS). No software updates needed (thanks -M-). Although I had changed the sensor myself in January I had the VW part receipt and VW therefore replaced the sensor under p and l warranty charging me a big fat ZERO and giving me another 2 years p and l on the new sensor!! THE NEW SENSOR HAS JUST FAILED AGAIN!! This time I believe I know what the problem is - I have been steadily leaking coolant on a daily basis for the past 9 months without finding any leaks whatsoever. I even changed the EGR cooler for a pressure tested 2nd hand unit which I also pressure tested before putting it on the car. I am now sure after several mornings of white whispy sweet smelling vapour oozing from the exhaust that I either have a cracked head (slightly unlikely as it is not a BKD engine but not altogether impossible and if so a new head is £££££££££££s) or more likely a leak from the water jacket side of the head gasket (less £££££s but still enough!). The coolant drop is overnight when cold and less when driving I assume due to expansion of the head metals thus compressing the gasket tighter. It also makes sense as 4 x G235 pre turbo EGT sensors have shorted within the past 2 years and the "wet" combustion would do cause the pre-mature death of the sensor as it is the first one the exhaust gases reach. When cold and under little throttle the EGR valve also diverts some of the wetter burn (until I am up to speed) to my throttle body which is coated in a wet sticky sooty paste but not as thick or dry as some deposits I have found inside diesel TBs however more like caramel than fudge if you can see the comparison. I have removed the TB, EGR pipes, inlet manifold and cleaned them all!! MPG has risen a little as a result but not to the 57.5mpg I had 18 months ago on a smooth run up to Yorkshire and back and the late 40s and early 50s mpg on a 40 mile run into work each day (AVERAGE 48mpg!). I will put the slight increase down to the clean however and am hitting lower to mid 40s on mpg now. Head gasket £600 to £750 from an independent (Checkatrade rated) and £975 by VW inc VAT. Trying to get them down as their radio add mentios price matching to locals! I'll take £775 inc VAT if I can get them there! Here's hoping!!! Should stop the sensor failures fingers crossed. Thanks to those here for the suggestions and advice.

UPDATE 2: VW wiped their hands and at over £2000 for just the usual head gasket and ancillaries I'm glad they did. Told me they would have to guarantee the work but that even doing the HG change might not cure my problem and may need further work at a cost or even a new head at VW prices. Car booked in for next Tuesday with an independent - strip down, head pressure test, skimming if necessary, new head gasket, new valve and injector seals, cambelt kit (belt, tensioner, water pump) rebuild and road test - basically the works. Total cost £1200 inc VAT (incl car hire of £60 for 7 days from garage). Kids are grown up so won't need to put an apple and an orange in their stocking this Christmas or anything else come to that!!! Might have enough left for a card or two!!

FINAL UPDATE?: HEAD IS CRACKED - my worst fear!! Cylinder 1 and 3 have cracks allowing the exchange of coolant to cylinders (hence rapid coolant loss) and exhaust gas to cooling system (hence burbling at return into expansion bottle). Head also warped but block ok. New cylinder head fitted and timing belt kit plus EGT sensor G235. Bit more to pay now! Car back and seems ok. No white smoke, decent mpg and still loads of torque although I have taken it easy for the past 2 weeks.

[tallpaulselfrid]

oh god! Major weekend depression sfter reading this! You have just described, word for word symptom for symptom me problem with my BMR! 3 egts in last year, white smoke, chip fryer smell, coolant loss, glow plug error....the lot. It's going to be an expensive few months...