VW Polo 1.2 TDCI EGR

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VW Polo 1.2 TDCI EGR

Postby mikeevans » Thu Dec 04, 2014 5:10 pm

I could do with some help regarding a problem I have with a 1.2 VW polo TDCI. Code 15536 EGR temp sensor (G98) P0405 Signal too low.. VW tell me that this relates to exhaust gas temp. sensors of which there are 3. My question is how do we test these sensors and what readings am I looking for. I hve connected the scope to all 3 sensor with a + - 5v scale but can't find any reading much over 1 v . Our code reader points towards EGR fault. Any help will be much appreciated.
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Re: VW Polo 1.2 TDCI EGR

Postby AuthorMike » Wed Jan 07, 2015 5:36 pm

Hi There,

How did you get on with this? Sorry for the lack of response.

Can you give year of manufacture, and do you know the engine code?

Thanks,
Mike Valentine
Technical Author @ Pico Technology UK
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Re: VW Polo 1.2 TDCI EGR

Postby mikeevans » Sat Jan 10, 2015 7:58 pm

Hi Mike and thanks for your reply. I dont have full car details but it is 6 months out of the 3 yr warranty and is a 1.2 3 cyl Diesel. We were getting conflicting information, Snap on indicating EGR valve temp sensor, VW telling us that the codes refered to the exhaust gas temp sensors, all of which are too expensive to replace without being able to diagnose the fault. As we could get no information we reluctantly refered the customer to VW. Spoke to the customer yesterday and she tells me that VW have told her that it needs a new EGR unit, and is booked in for replacement soon. Next time we'll ignore VW advice and pay more attention to Snap On but we still need to be able to pove that parts are faulty before we replace.
Regards Mike
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Re: VW Polo 1.2 TDCI EGR

Postby KimAndersen » Sun Jan 11, 2015 12:20 pm

HI there

After I have read your thread a couple of times I became a little confused over the DTC description your are getting on your Snap On tester.

Firstly I don't think the DTC description (G98) are interpreted correctly from the ECU data on your tester.

Why not !!! because when i look at Self-study Programme 465 where the system are described in details are there are no description of this sensor (G98), there are 3 sensors as you already have mentioned with the following names - exhaust gas temperature sender (G235 - G495 - G648).

The description you got from local volkswagen dealer regarding the diagnostic trouble code 15536 EGR temp sensor (G98) sounds more likely to be correct, that its a exhaust gas temperature sensor and not egr valve temp sensor.

I might help you with the interpretation of the voltage readings from the exhaust gas temperature sender (G235), if you read the last part of my case study regarding " How to measure a Bosch LSU 4.9 wideband lambda sensor " https://www.picoauto.com/support/post32289.html#p32289 where I have logged some live data readings from this sensor (G235). The case study are based on a Jetta 2.0 TDI with DPF (diesel partikel filter) which basic are the same as fitted on your Polo 1.2 TDCI system.

From your own experience of measuring these exhaust gas temperature and the result you were getting of 1 volt on all these sensor - would I say, that this are really low voltages readings.

There may be a link between the low voltage readings from exhaust gas temperature sensor (G235) and the EGR-system. If the egr valve system are hanging will there be some disruption of exhaust gas flow through the exhaust system.

Regards
Kim :wink:
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