# Help! Weird fault code issues **SOLVED!**



## asahartz (May 24, 2014)

I've posted about this before, but never got anywhere with solving it. Now the car's failed its MOT due to them, and I need to fix this pronto.

Using VCDS lite I get a consistent set of engine fault codes - I can clear these but as soon as I start the engine they're back.

17833 EVAP Purge Valve (N80) short to ground
P1425 - 35-00 - -

17525 Oxygen (Lambda) Sensor Heating; B1 S1 short to ground]
P1117 - 35-00

17861 Exhaust gas temperature sensor 1 open/short to B+ 
P1453 - 35-00

16486 Mass Air Flow Sensor (G70): Signal too low
P0102 - 35-00

17523 O2 Sensor Heater Circ.,Bank1-Sensor1 Short to Ground
P1115 - 35-00

17522 Bank1-Sensor2 Internal Resistant too High 
P1114 - 35-00

17511 Oxygen (Lambda) Sensor Heating; B1 S1: Performance too low
P1103 - 35-00

17963 Boost pressure control - Upper limit exceeded
P1555 - 35-10

In addition, I have an intermittent ABS light, and the code that keeps coming back here is
01314 - Engine Control Module
79-00 - Please check fault codes

Now why is the ABS getting a fault from the ECU?

I had the car in for service at a local VAG indy, who said they'd never seen a car with so many faults. However I'd only asked them for a service, so they didn't investigate beyond clearing all the codes. They did suggest looking for a common earth fault, and studying the wiring diagram says these all earth in the engine bay under the battery - I've cleaned this up and retightened the nut but no difference.

Now here's where it gets weird. I've checked the EGT sensor with a multimeter and it's definitely not open or short circuit. Neither is the N80 valve.
In addition, I just fitted a new B1 S1 lambda and took it back for a retest - it failed again with the same lambda fault (the CO reading is around 6% against 0.3% max), and the 17511/17523 code has come back even having cleared it. Now I'm assuming my new sensor isn't faulty, so it looks like a possible wiring fault, or, heaven forbid, the ECU. But where? Any thoughts on this? Please?


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## Stevey83 (Oct 16, 2011)

A faulty MAF can show all sorts of fault codes. Have you checked it's working ok.


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## asahartz (May 24, 2014)

Stevey83 said:


> A faulty MAF can show all sorts of fault codes. Have you checked it's working ok.


But surely not take out the lambda sensor as short circuit? In any case I've had the same results with the MAF unplugged.

Later I'm going to start tracing the wiring back from the lambda.

I also had another look at the earth point under the battery, and one of the terminals (with a thick wire) showed some corrosion. I cut it off to fit a new terminal, and on stripping back the insulation, found that the wire had oxidised. Now I know these cars are getting old now, but that's not something I usually see until cars are quite a bit older - the wiring in my '89 Mini hasn't degraded that much yet, so that's worrying. I've soldered as well as crimped the terminal, and I'm tracing that earth wire up and fitting a second one parallel to it.

At least wiring is my strong point.


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## Skeee (Jun 9, 2009)

Sorry don't have any experience on that condition- but as you're already doing I'd look at a wiring diagram to see what is common for all the listed faults.

According to this it could be the ECU. Have you checked the ECU connector is clean and dry?
http://wiki.ross-tech.com/wiki/index.php/01314
 01314 - Engine Control Module
01314 - Engine Control Module: No Communications
Possible Causes
CAN-Databus Wiring/Connectors from/to Engine Control Module faulty
Fault(s) stored in Engine Control Module
Engine Control Module recently flashed or re-mapped

Possible Solutions
Check CAN-Databus Wiring/Connectors from/to Engine Control Module
Check Measuring Value Blocks (MVB)
Usually Measuring Value Blocks (MVB) 125+ show the current Communication Status

01314 - Engine Control Module: Check DTC Memory
Possible Causes
Fault(s) stored in Engine Control Module

Possible Solutions
Check Engine Control Module for Fault Codes

Special Notes*
Engine Control Module stored a Code which influences other Control Modules Functionality.
To clear this Fault Code you will need to correct the Problem in the Engine Control Module first. *


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## asahartz (May 24, 2014)

Yes, I've checked the ecu connectors and sprayed them with a proper electrical contact cleaner.

I'm making progress anyway, I've lost the B1 S1 lambda fault codes. When I got the car the excess cable length from the lambda sensor had been tie-wrapped to the strengthening bar that goes across the strut tops, so in replacing the sensor I did the same thing. It seems that this is enough to throw up the sensor code! Having removed the strut brace for access the codes have gone. So I've fastened the cable away in a different position.

I still have the B1 S2 lambda fault so I'll order that one now. Looks as though maybe dodgy MAF too.

And checking the wiring diagrams shows that the EGT and the N80 are connected - disconnecting either of those throws up "N80 open circuit", so I'll investigate that further.

I don't know if fixing these codes might affect the ABS code too. Right now the battery's out while I fix the earthing issue, so that will have to wait for later.


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## Stevey83 (Oct 16, 2011)

You may have a break in the wire if moving it has rectified it.


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## asahartz (May 24, 2014)

Stevey83 said:


> You may have a break in the wire if moving it has rectified it.


No, the fault code was showing short to ground, and this was the new cable. I'm thinking that strapping the cable to an earthed part was giving just enough induction to fool the ecu into thinking it was a short.


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## ades tt 180 (Jun 19, 2011)

Sounds like that lambda is the wrong one...The wire should be just long enough to reach its connector...not sure what the difference is between the front and rear lambdas though.


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## asahartz (May 24, 2014)

It was exactly the same as the one I took off.


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## ades tt 180 (Jun 19, 2011)

I replaced both my lambdas when I put my 3 inch d/p on and the front one deffo had a shorter wire than the rear one.


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## asahartz (May 24, 2014)

It's shorter than the rear one, yes, but there's still a lot of spare cable.

Anyway, that code's sorted out, and I've ordered a rear lambda now and reserved a new MAF at my local ECP. Hopefully that should be enough to get it through the MOT, then I can sort out the remaining issues when the bank account recovers a bit!


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## bobbobb (Dec 24, 2008)

try to make sure you get a bosch maf as i have had issues with others.

i know its a really daft question but have you had battery off and charged it off car then put it back on this solves a lot of strange codes that wont clear a lot are down to poor battery


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## asahartz (May 24, 2014)

bobbobb said:


> try to make sure you get a bosch maf as i have had issues with others.
> 
> i know its a really daft question but have you had battery off and charged it off car then put it back on this solves a lot of strange codes that wont clear a lot are down to poor battery


It's a Bosch maf, yes, collected today.

I don't think it's down to the battery, this car is driven 40+ miles every day. The codes will clear, they just return as soon as the engine is started. But I'll bear it in mind.


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## asahartz (May 24, 2014)

First I replaced the pre-cat lambda. That 17525 fault code went - but occasionally showed up again - strange.

Then I replaced the MAF with a Bosch recon part. Still the 16486 "MAF signal too low" would pop up sometimes.

Finally I replaced the post-cat lambda. But the fault code 17522 wouldn't go and occasionally I would see 17523 as well.

The Gastester reading was also still stratospheric, so it was no good going back to the MOT station.

In desperation I examined the circuit diagrams for a common area where I might locate a short. Because the diagram stretched over 3 pages, I decided to draw out the bits that were showing faults on a sheet of paper. In doing this I found that all these components had a common connection to fuse 43. So I checked fuse 43 - and there wasn't one! Some previous keeper had removed it for some unknown reason - god knows why. :roll: I put in a fuse, checked the fault codes, and bingo! No engine fault codes at all! What's more the Gastester reading had fallen to near-zero!

Back to MOT - Pass! Yay! 

So anyway, I have shelled out close to £200 in parts for the sake of a fuse.  And nobody here or at my VAG indy even thought of that either. So I guess the lesson here is, if you have a bunch of weird fault codes, start at the fusebox - it could save you a lot of time & cash.


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## PeterW (Dec 30, 2014)

good thinking

now you know why previous owner sell the car


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## asahartz (May 24, 2014)

I don't think the previous owner had much of a clue. And to be honest, I still think I've got a decent standard TT which I can sort quite easily now.


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## Skeee (Jun 9, 2009)

asahartz said:


> First I replaced the pre-cat lambda. That 17525 fault code went - but occasionally showed up again - strange.
> 
> Then I replaced the MAF with a Bosch recon part. Still the 16486 "MAF signal too low" would pop up sometimes.
> 
> ...


 Excellent well done! Glad you sorted it and for something so simple. Take consolation in the fact it's much more satisfying when you've fixed it yourself and also in the fact that MAFs and Oxygen Sensors do wear out so you haven't wasted all that money.

I did mention to look for something common but didn't have time/cba to search the diagrams as busy on other projects at the mo. Thanks for posting the solution (not everyone does!) hopefully it will help others!


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## asahartz (May 24, 2014)

Well true, the packaging with the Lambdas mentioned that they should be replaced at 160k and my car's done 143k (it's still in good nick for it), so the money's not wasted, I know that. But I daren't tell my wife that a fuse would probably have got it through the MOT!

Oh, and now my windscreen's cracked where a stone hit the edge. Never rains, does it?


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## John-H (Jul 13, 2005)

It did sound like a positive side common fault with all the short to ground codes. Well done for being systematic and tracing it to the cause [smiley=thumbsup.gif]


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## asahartz (May 24, 2014)

Well I thought the car went well before, but it's just amazing now! Whoosh... :lol:


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