The dreaded "Short to ground - MIL ON"

[alicat_vag]

Hi all,
My first to the forum, but been reading for quite a while (got several older VAG cars in various states of continual "tinkering and problem fixing")! Sorry this is so long...
Got a curious problem with my latest acquisition (FOC gift!), a Mk5 Golf 1.4 FSI, BLN engine, VIN: WVW1KZ6B024954. Check engine light comes on, so checked with VCDS, and the relevant VCDS scan excerpts are:


Saturday,31,July,2021,20:44:28:05031
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 15.7.1.0 (x64)
Data version: 20150904
www.Ross-Tech.com


VIN: WVWZZZ1KZ6B024954 License Plate: SK55WPF
Mileage: 155110km-96380mi Repair Order:


--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: 1K (1K0)
Scan: 01 03 08 09 15 16 17 19 25 42 44 46 52 56


VIN: WVWZZZ1KZ6B024954 Mileage: 155110km-96380miles


00-Steering Angle Sensor -- Status: OK 0000
01-Engine -- Status: Malfunction 0010
03-ABS Brakes -- Status: Malfunction 0010
08-Auto HVAC -- Status: Malfunction 0010
...


-------------------------------------------------------------------------------
Address 01: Engine Labels: None
Part No SW: 03C 906 056 AJ HW: Hardware No
Component: MED 9.5.10 00 7002
Revision: 00000000 Serial number: VWZ7Z0E2302841
Coding: 0000071
Shop #: WSC 00046 412 98304
VCID: 6BD25F834A96576698-803E


3 Faults Found:
005157 - EVAP Purge Valve (N80)
P1425 - 002 - Short to Ground - MIL ON
004135 - Intake Manifold Tuning Valve Control Circuit
P1027 - 002 - Short to Ground - MIL ON
005728 - Coolant Fan Control 1
P1660 - 002 - Short to Ground - MIL ON
Readiness: 1110 0101


-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 1K0-907-379-MK60-F.lbl
Part No SW: 1K0 907 379 AC HW: 1K0 907 379 AC
Component: ESP FRONT MK60 0101
Revision: 00H11001
Coding: 0019073
Shop #: WSC 00706 210 87584
VCID: 73E247E312A68FA650-8026


1 Fault Found:
01314 - Engine Control Module
013 - Check DTC Memory - Intermittent


-------------------------------------------------------------------------------
Address 08: Auto HVAC Labels: 1K0-820-047.lbl
Part No: 1K0 820 047 DF
Component: Climatic PQ35 090 0505
Shop #: WSC 00000 000 00000
VCID: 6BD25F834A96576698-803E


1 Fault Found:
00229 - Refrigerant Pressure
002 - Lower Limit Exceeded


-------------------------------------------------------------------------------
...


ABS one is, I think, a vestige of the recalled ABS replacement done by PO, it clears, currently not a worry for me?
Refrigerant Pressure, also not something I am worrying about, just the check engine/fan availability that is bothering me.


I did a fuse check, this car has "Fuse box low", and SB24 had blown; all other SA and SB were intact; I didn't check SC.

I put another 10A in to SB24, and it blew immediately (ignition NOT on), and I'm getting 12.8v from both blades/top positions.


Looked up a fuse reference Volkswagen Golf mk5 (1K) (2003 - 2009) - fuse box diagram - Auto Genius, and it says it protects many circuits:
F24 10A
F265 – Map-controlled engine cooling system thermostat
J293 – Radiator fan control unit
N18 – Exhaust gas recirculation valve
N80 – Activated charcoal filter solenoid valve 1
N156 – Variable intake manifold changeover valve
N205 – Inlet camshaft control valve 1
N316 – Intake manifold flap valve
V157 – Intake manifold flap motor


So J293 means my fans are not being regulated, I interpret, not good...


Next, I disconnected the connectors from purge valve, MAP, IAT, flap potentiometer, TB, EGR, camshaft sensor, FPR, disconnected the T4 connector to the fan assembly, tried again, fuse SB24 still blows every time I replace it, so I'm interpreting that as none of those sensors are shorted internally. Fans DO work when powered directly from battery, so I think it is NOT the inbuilt fan control unit shorting the fuse: have fans, but the ECU just cant turn them on!

I dont think this engine has a flap motor in the fuel rail/ports, pretty sure its all done by manifold vacuum (the con rod to the flap potentiometer moves freely)???

Then I disconnect battery, touch battery leads for 15 sec, reattach all sensor connectors etc, insert fuse, reattach battery leads, fuse doesn't blow.
Turn ignition on, TB does its usual clicking and whirring etc, still fuse does not blow.
Rescan with VCDS, clear all the expected "missing sensor" DTC, ignition off, ignition on, rescan with VCDS, no DTC apart from the A/C pressure one, ignored, so all good.
Fuse is rechecked, it's OK, so start engine, sounds fine, OK for about a second or so, fuse blows, check engine light comes on, but still engine sounds fine.
Rerun VCDS, and I have got two of the three "Short to ground" DTC again (nothing else, other than the A/C pressure)


005157 - EVAP Purge Valve (N80)
P1425 - 002 - Short to Ground
004135 - Intake Manifold Tuning Valve Control Circuit
P1027 - 002 - Short to Ground


Of course, since SB24 has gone, I can't do any output tests in VCDS...!


The SB low A1 relay, a 458 one, gets pretty warm, but I am thinking that if this was not good, then I wouldn't have any ECU functionality at all (i.e. no start, nothing) as it powers the ECU?


So, this is more or less as far as I have got, other than find and start trying to figure out some wiring diagrams for the BLN engine.... (recommend the Ross-Tech tutorials on reading diagrams, REALLY good!)

I don't have the eBahn clicky versions (nor can I find!), only what I purchased from Portal-Diagnostov.com; Haynes of course doesnt have the current flow diags I need for this....

I also have elsawin in a VM off fleaBay, so I am wondering if it is best to start at SB24 and work backwards, or to start "disassembling the wiring" from N80 towards the ECU, looking to see where the earthing is happening; it's all still wrapped up from its initial VW wiring, and I can see no evidence of rodents/damage/scuffing. I've tried various things with my multi tester and light, but not really any the wiser, perhaps/probably not looking for the correct thing!?

I did have the intake manifold off just before I had the shorting issue, and so hope that it is not something I have inadvertently caused by stretching a wire or similar act of utter numptyness!

I've not done this kind of troubleshoot before (definitely more happy with a spanner), so wonder what you good folk would recommend should be my starting point?

Apologies again for the length, but tried lots of things with no benefit, other than a gain of some knowledge!

Hope you can help, the car seems to drive etc fine, but I really don't want to leave it as it is (and it wont pass MOT...).
Cheers!
al

[FLAPPERJACK76]

Disconnect the n80 valve evap, does the fuse blow with it disconnected?

Sent from my SM-G970F using Tapatalk

[alicat_vag]

Yes, i tried disconnecting purge valve N80, fuse still blows, so i am suspecting the short might be closer to the fuse?

[FLAPPERJACK76]

What you really want is the wiring diagram showing everything that shares fuse 24. The area between the starter motor and the ebox are common areas for wiring rub in my experience.

Sent from my SM-G970F using Tapatalk

[alicat_vag]

Yes, that is what I need indeed!

However, elsawin and the others that I mentioned using unfortunately don't seem to do a "fuse-centric" option, I was just hoping that there might be a magic/quick way to not have to undo all the neatly wrapped wiring there!!

Have contemplated getting the S&G Short Finder 25100 on fleaBay but not sure if others have used and can recommend it? S&G Tool Aid Short Finder 25100 | eBay

I'll start where you suggest, there are a few relevant wires with a common going into the T14a (see my modified SVG pic below), unfortunately following along to wire 71 suddenly becomes a lot more challenging without a hyper-linked wiring diagram programme, hence fear of adding more damage to what I already have...!
Thanks!
A

N80.3fd4c754db1198a7e0053f69c50b1510.jpg

[Crasher]

I need to check at work but I remember it being the clutch master cylinder Hall sender, you can download all the dealer level data from https://erwin.volkswagen.de/erwin/sh...7C088.ASTPVWE1, if you get organised with a print to pdf program and sufficient disc space, you can download everything to do with your car within the 7 Euro per hour or maybe two, a whole day is only €30.

[alicat_vag]

Thanks, that would be most helpful. I will also have a look at erwin; do you have an idea (rough) as to how much disk space one might need for a Mk5 "complete set"?

Update: yellow box 71 on the diagram above leads to fuse SB24, so at the moment, have bitten the bullet and undoing the loom downstream of the T14a connector (fuse stays intact if I disconnect T14a, but engine doesn't start anyway as coils powered via a wire in this connector... need to get a de-pinning tool!).

Power wiring (blue, red trace) looks ok from T14a to the purge valve connector, so now gonna have to take the inlet manifold off yet again to get to the flap valve solenoid wiring...

I'll also need to re-wrap the loom after (if) I find the earth; is Tesa tape the favoured way to do it (another thing I have never done!)?
thanks again!
al

[Crasher]

I downloaded about 20 current flow files for a T6 and it was 71 meg.

[alicat_vag]

thanks

[alicat_vag]

So, in the spirit of all things forum, an update on this: all solved, yaay! No blowing fuse, no check engine, radiator fans working, all tickety-boo!

What was the cause? Me, sadly!

Whilst reinstalling the inlet manifold, I tightened the bolt holding conduit that contains the wiring for the injector and manifold flap valve without having a clear sight of what I was doing, my glasses were in the house....
If I was asked to make a continual earth connection again, I really don't think I could have done it anywhere near so well.

Guess which is the power line.... yes blue with a red trace!

IMG_0210.jpg

What did I learn?
1. importance of wiring diagrams, they work, thanks Crasher and elsawin
2. how to read wiring diagrams, thanks Ross Tech training
3. bought and used de-pinning tools, enabled me to narrow down the location of the problem, thanks Amazon
4. that no matter how often you think you have checked things, do it one more time (from a different angle... in full daylight... with your glasses on if you need them.... thanks....??)

a