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Post by Joepublic on Feb 21, 2019 12:40:50 GMT 1
carmechanics.proboards.com/thread/5278/vag-egr-codesI had a bit of bother with an earlier VAG TDi a few weeks ago, codes cleared and they came straight back, removed and refitted the fuse from the under bonnet fuse box and the light hasn't reappeared since. I had lighting issues a few weeks earlier with 7 codes and with help off here I found a fuse in the same fuse box showing arcing on the blade. Worth checking the basics
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gregg
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Post by gregg on Feb 21, 2019 20:04:25 GMT 1
Well lads just a wee update. Got chance of trying a new maf sensor today. Still the same so dont think its causing my trouble. Strange thing is after i fitted it and started engine up, within 30 secs glow plug light came on and logged p0297 boost pressure sensor signal too low and another fault code saying a fault in another module was preventing a self test. This coincided with tyre pressure light and esp light coming on. They all cleared again but seemed strange.
I have pictures of fault.codes.and live data i got out of ecu after test drive so il upload them here as soon as i am home.
Tia
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Deleted
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Post by Deleted on Feb 21, 2019 20:29:09 GMT 1
I don't profess to remember the specifics/details now, but one guy on the auto electrics course had an Audi 2.0 TDI with an air maf related issue and after testing at college even though no apparent fault indicated it was at fault, he went out and still bought one only to conclude later that after fitting and no effective repair to thought the PCM was then the cause! Well lads just a wee update. Got chance of trying a new maf sensor today. Still the same so dont think its causing my trouble. Strange thing is after i fitted it and started engine up, within 30 secs glow plug light came on and logged p0297 boost pressure sensor signal too low and another fault code saying a fault in another module was preventing a self test. This coincided with tyre pressure light and esp light coming on. They all cleared again but seemed strange. I have pictures of fault.codes.and live data i got out of ecu after test drive so il upload them here as soon as i am home. Tia How do we say it, well I told you so  |
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Post by chippie on Feb 21, 2019 20:59:26 GMT 1
Remind me not to gamble...  How did the boost pressure measurement go? Keep us updated , I'd love to hear how this is resolved.. |
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gregg
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Post by gregg on Feb 21, 2019 21:08:43 GMT 1
Lol only good thing is i can send maf back again so not too bad. I have picture of the live data cant mind readings off hand. Il be back home soon so il update my pics then and see what you all think.
On an off chance i rang an audi dealership and gave them chassis number but no outstanding faults or updates are due atm so rules out that possibility.
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gregg
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Post by gregg on Feb 21, 2019 22:57:51 GMT 1
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gregg
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Every day is a school day.
Posts: 72
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Post by gregg on Feb 21, 2019 22:59:44 GMT 1
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gregg
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Every day is a school day.
Posts: 72
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Post by gregg on Feb 21, 2019 23:07:41 GMT 1
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gregg
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Posts: 72
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Post by gregg on Feb 21, 2019 23:09:58 GMT 1
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gregg
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Every day is a school day.
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Post by gregg on Feb 21, 2019 23:13:12 GMT 1
These 3 fault codes are now present after the new maf sensor was put on. I'm now scratching my head here as to why cylinder 3 pressure sensor has flagged up again. I would have thought a new part wouldn't be faulty after just two weeks, although not unheard of. i will hopefully get a boost pressure reading tomorrow as i couldn't find my own gauge today.
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Post by chippie on Feb 21, 2019 23:18:58 GMT 1
Cyl 3 glo plug goosed? Try swapping with another cylinder...Wiring ok? I guess it must be if you have a within range reading...i.e not 250bar plus...
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gregg
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Every day is a school day.
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Post by gregg on Feb 21, 2019 23:24:24 GMT 1
Cyl 3 glo plug goosed? Try swapping with another cylinder...Wiring ok? I guess it must be if you have a within range reading...i.e not 250bar plus... Brand new less than 2 weeks ago, can try swapping it tomorrow to see though not sure if it would have to stay at cyl 3 if ecu is coded to take a pressure reading from it? |
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Post by chippie on Feb 21, 2019 23:33:59 GMT 1
If you move the gp from 3 to another pot and recode the ecu, if the fault moves then the gp is faulty....surely?
Can you remove the ecu and get it tested to exhonerate it?....
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Post by valhalla on Feb 22, 2019 1:03:42 GMT 1
How do we say it, well I told you so Possibly a slightly unfair statement! After all, your first thought when you look at data like the above is not to blame the PCM for a higher airflow than is normal, you look for leaks and some sort of correlation with a known good MAF.
In this case, if the MAF can be returned, or used for another car, it was a good thing to do. It was a logical step to take, and I would have gone for that one immediately after checking all of the intake tracts for voids into the exhaust or atmosphere, as that is the most probable culprit and easily seen with a smoke-leak-test machine. After that MAF.
The very last thing you suspect, because it is expensive and illogical, is the PCM. Especially in this case. The airflow reading on one of these systems is by PWM (pulse width modulation) and not an analogue signal, hence it is less likely that the signal is corrupted by the MAF circuitry or a PCM impedance error.
A correlation with an external boost pressure sensor will exonerate the MAP sensor (or not, as the case might be) and then it will be down to double-checking the intake tracts.
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Deleted
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Post by Deleted on Feb 22, 2019 19:42:23 GMT 1
How do we say it, well I told you so Possibly a slightly unfair statement! After all, your first thought when you look at data like the above is not to blame the PCM for a higher airflow than is normal, you look for leaks and some sort of correlation with a known good MAF.
In this case, if the MAF can be returned, or used for another car, it was a good thing to do. It was a logical step to take, and I would have gone for that one immediately after checking all of the intake tracts for voids into the exhaust or atmosphere, as that is the most probable culprit and easily seen with a smoke-leak-test machine. After that MAF.
The very last thing you suspect, because it is expensive and illogical, is the PCM. Especially in this case. The airflow reading on one of these systems is by PWM (pulse width modulation) and not an analogue signal, hence it is less likely that the signal is corrupted by the MAF circuitry or a PCM impedance error.
A correlation with an external boost pressure sensor will exonerate the MAP sensor (or not, as the case might be) and then it will be down to double-checking the intake tracts.
Diagnostics are not the easiest to pinpoint and get it correct first time every time, however that said, if somebody else has had similar problems and already been down the road you are travelling, then changing parts that are not confirmed as the cause of the fault is timely, costly and most importantly not fair on other people who buy your secondhand MAF as new which "Might" now have a problem on it after being used. For me there is no last thing or suspects, it is as I was always told in my training days, test all the sensor inputs/outputs to confirm/dismiss a problem. I do however agree that time has moved on and that vehicles are very much more complicated now than ever before, hence using forums for advise. Had A/D of been more thorough in their technical data I'd of supplied a test plan for gregg to follow, but as I advised him A/D are not that good with their data these days so I could not follow through. I do however have loads of previously purchased VW/Audi data that I have on file, so if gregg chooses to supply specific data of his car so that it can be correctly identified then I could search my archives and see what I have to help further. I'm not a ready believer of "Parts darts" valhalla so on this point I must disagree that trial and error is not the best way forwards, as the evidence has now shown conclusively. I don't wish to upset anyone but must therefore be able to share my point of view from the trade perspective. |
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