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Thread: Polo 9n3 fuse F14 blown

  1. #1
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    Polo 9n3 fuse F14 blown

    Hi,
    I have a polo 9n3 1.4 TDI with what I think is a BWB engine. Recently the engine light came on and the car took a long time to turn over before starting. After getting the error messages scanned and replacing / cleaning a few components along the way, I found fuse F14 had blown. Iím aware the fuse covers the EGR, intake manifold flap and camshaft position sensor (hall sender?), which Iíve almost exhaustively checked are working, but there seems to be something else that blew the fuse and is still creating a short circuit with fuse F14 replaced. (Battery is running out very quickly with a new fuse in F14). Can someone tell me what else is on this circuit? Various posts online refer to a crankcase breather, or SAP relay, but iím not sure where these are or how to diagnose them. Any help would be gratefully received. Thank you 😊

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    Administrator Crasher's Avatar
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    Could you PM me your REG and I will look into it at work.
    2003 Skoda Octavia VRS Estate. APR 98RON remap, APR R1 diverter valve, Jetex exhaust, K&N panel filter, 7.5x18 Alutec Monstr wheels with 225/40 18 Uniroyal Rainsport 3 tyres.
    2006 Polo GTI 1.8T, APR 95RON remap
    1988 Golf 2 GTI 16 valve, 2.2 with Weber Alpha injection
    1983 Golf 1 GTI 8 valve, 2 litre with Eurospec racing 42/36 head
    1972 1302LS auto 1641cc conversion

    Vile Invention

    Dark was that day when Diesel conceived his grim engine that begot you, vile invention, more vicious, more criminal than the camera even, metallic monstrosity, bale and bane of our culture, chief woe of our Commonweal. How dare the Law prohibit hashish and heroin yet license your use, who inflate all weak inferior egos? Their addicts only do harm to their own lives: you poison the lungs of the innocent, your din dithers the peaceful, and on choked roads hundreds must daily die by chance-medley. Nimble technicians, surely you should hang your heads in shame. Your wit works mighty wonders, has landed men on the Moon, replaced brains by computers, and can smithy a "smart" bomb. It is a crying scandal that you cannot take the time or be bothered to build us, what sanity knows we need, an odorless and noiseless staid little electric brougham.

    W.H. Auden (1907-1973), A Curse:

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    Administrator Keithuk's Avatar
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    First posts normally go in introductions else you could get a free fix and we never see you again!!!

    Your car spec says 0, only what I've added from this post minus the year.

    To find any circuit diagram join https://erwin.volkswagen.de/erwin/showHome.do for a day to save everything as a PDF file. Or you find someone with ElsaWin to do the same.
    2010 Golf GTD (170) CBBB, 5 Door, Shadow Blue (P6/D5Q), Transmission Code: KXZ, Flat Tyre Indicator, Basic Protection Pack + VCDS.


  4. #4
    Administrator Crasher's Avatar
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    Fuse SB14 powers the vacuum control unit which incorporates the N75 wastegate solenoid and the N18 EGR solenoid plus as you say the G40 camshaft position sensor. What it also powers is the V157 intake manifold flap motor which is mounted in front of the EGR valve, VAG part number 045 128 063 G which has a VAG retail price of £571.20. Euro Car Parts sell the exact OE Siemens VDO part for £554.99 which is daft BUT you can get the ont tinterweb for less than £200 for a proper VDO part or less for an aftermarket copy but I would strongly recommend VDO.

    Unless it is a wiring short to ground I would be 99.99% sure that it is the V157 at fault, disconnect all the devices and replace the fuse, if it blows you have a wiring short to ground. If it doesn't, reconnect the V157 and I would be extremely surprised if the fuse did not blow.

    2003 Skoda Octavia VRS Estate. APR 98RON remap, APR R1 diverter valve, Jetex exhaust, K&N panel filter, 7.5x18 Alutec Monstr wheels with 225/40 18 Uniroyal Rainsport 3 tyres.
    2006 Polo GTI 1.8T, APR 95RON remap
    1988 Golf 2 GTI 16 valve, 2.2 with Weber Alpha injection
    1983 Golf 1 GTI 8 valve, 2 litre with Eurospec racing 42/36 head
    1972 1302LS auto 1641cc conversion

    Vile Invention

    Dark was that day when Diesel conceived his grim engine that begot you, vile invention, more vicious, more criminal than the camera even, metallic monstrosity, bale and bane of our culture, chief woe of our Commonweal. How dare the Law prohibit hashish and heroin yet license your use, who inflate all weak inferior egos? Their addicts only do harm to their own lives: you poison the lungs of the innocent, your din dithers the peaceful, and on choked roads hundreds must daily die by chance-medley. Nimble technicians, surely you should hang your heads in shame. Your wit works mighty wonders, has landed men on the Moon, replaced brains by computers, and can smithy a "smart" bomb. It is a crying scandal that you cannot take the time or be bothered to build us, what sanity knows we need, an odorless and noiseless staid little electric brougham.

    W.H. Auden (1907-1973), A Curse:

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  6. #5
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    Hi Crasher, thanks for the research. I immediately suspected the V157 was the problem when the engine management light first came on. An initial investigation of the presenting symptoms seemed to fit with this. As such, I took off the V157, cleaned it and refitted. I also used the access to clean the EGR in situ. There was a degree of carbon build-up, but I wouldn't say it was inhibiting function. With the engine light remaining, I then replaced the camshaft position sensor, as I was told by a garage that this was the issue that fitted the diagnostic they'd done. This was all before I knew that fuse SB14 had blown. Now that I've replaced the fuse, it seems to be holding steady, and the V157 appears to be working okay (it flickers slightly when I turn the ignition to the pre-turn over/primed position) but when I go to start it struggles to kick and then stalls immediately (with the fuse out it struggles to start but the runs okay, albeit with the engine light on and all errors present). This makes me think that the V157 is working okay. I'm pretty sure I was wrong to replace the camshaft position sensor and so I've just reverted to the original. I'm now fighting battery issues though, so haven't been able to check whether it was a bad / incompatible replacement sensor that causes the car to struggle to start as I've not tested the car with the original sensor and a replacement fuse. I'm aware that if I can get past the starting issue with the fuse replaced, I can fully check the V157, as I can see what it does at switchoff. However, I don't think this would explain what blew the fuse initially. If the V157 is okay (initial signs suggest it is) and the original camshaft position sensor was okay, have you got a suggestion for what could have initially blown the fuse?
    I should mention, while digging around I have noticed a small hole in the #2 vacuum line. Not sure if this is relevant
    2 x Polo 9N3 1.4 TDI Match 70 (58 reg & 59 reg)

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