How to test an exhaust gas tempoerature sensor?

[petrolhead63]

Long story this, it follows from previous woes of sensors, DPF etc. The 2.0 tdi 170 quattro got sorted by cleaning DPF and replacing the temperature sensor one eventually, it came out of limp mode and all lights off. Plus cleaning a stuck EGR etc etc. It drove for 1000 miles or so fine.
Then the glow plug and MIL light come on again, my scan indicates again the temperature sensor one, bank one. This was replaced just after buying the car two years ago and again very recently.
It may be a duff sensor? wiring looks ok.
does anybody have an checks i can make for resistance values cold and as it warms up using a multimeter?
It is a swine to change and I do not want to swap it again if it is testing ok as a sensor and the issue is elsewhere on the loom/ecu.
Thanks for any help.

[Crasher]

The BMM engine can be very trying, first of all, is the MAP standard?

[petrolhead63]

Yes it has been trying in our 2 year ownership.......one of the worst cars we have ever had and its lowest mileage we bought for a long time too! from recollection its a CBBB code engine and as far as I know it is all bog standard. One previous owner with all its records prior to us.

[Crasher]

The CBBB is usually OK, the previous BMN was an awful engine, which year is it?

[petrolhead63]

Hi Crasher, thanks as always.....first reg. December 2008, CBB engine number on log book though CBBB is on the sticker in the service book. The code wont clear and stay out at all, so I wonder whether to simply invest in another temp sensor and plug it in out the car cold then see what happens on a start up/fault clear etc. DPF light not back and it runs fine...for now
Its another £50-60 but less than losing it to a garage straight away.
My scanner is VW/audi but not a full vag-com.

[Crasher]

It will be a 2009 model, which EGT sensor is at fault, 1, 3 or 4?

[petrolhead63]

EGT Sensor 1 bank 1. so I believe it to be the one tucked under the DPF/Cat area which I changed and sorted it for a bit! That was done on warranty just after buying it and that was what started issues again before hte DPF/limp mode fiasco! I changed it and that code cleared then we did the DPF clean to get it out limp mode and the DPF light off.
As said it drove no lights for 1000 miles or so, now again the glow plug light blinking and MIL light, scans as temp sensor 1 bank 1 again.
I do confess perhaps the sensor was of dubious quality! we were throwing things at it and it did prove the fault as the code cleared however maybe it has failed early.
Oh fogot to add it also had a new pressure snesor switch on the DPF seeing as it was giving bizaar readings out of spec. That is good quality!

[FLAPPERJACK76]

What you need to look at is live readings of all exhaust gas temperature sensors, when the engine is cold and not been started. All should be about the same any anomalies in temperature and thats your problem. Then once that is sorted and faults are erased make sure your dpf offset value is zero. Then a forced regeneration.

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[Crasher]

The CBBB EGT 1 is in the manifold



CBBB EGT system

1) Turbocharger
2) Control pipe
3) Particulate filter
4) Nut
5) Bracket bolted to particulate filter
6) Hose
7) Bracket for exhaust gas pressure sensor G450
8) Exhaust gas pressure sensor G450
9) Bracket
10) Bolt
11) Bolt
12) Exhaust gas temperature sender 3 G495
13) Lambda probe G39 with Lambda probe heater Z19
14) Exhaust gas temperature sender 4 G648
15) Exhaust gas temperature sender 1 G235

[FLAPPERJACK76]

And if you replace no1 egt make sure the long metal tip is not touching any part of the turbocharger when you tighten it up, as you will get false readings.

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