# Replacing a cracked coil pack wiring harness.



## westcoTT (Aug 30, 2009)

I had noticed that my wiring loom looked pretty rough after a coil pack decided to die on me. The most obvious signs were the splitting of the PVC covering around the Earth wire and around the trigger control wires on the big connectors which attach to the coil packs.
Also I had had issues with the car sounding if it was running on 3 cylinders on start up, although it was an intermittent fault and only did it on cold days.

Anyway

Due to plans to make the car more track day with a bigger turbo conversion I needed a better harness than a standard replacement.

So. I fitted a Phaar-drive high performance harness which is made from the same stuff you find on F1 and WRC rally cars.
Its also a lot thinner that the original, can handle the heat which is great, and as a bonus cleans up the top of the engine.

The process is the same for those fitting a standard replacement too.

Once I had fitted the replacement loom I pulled the old one to pieces to see just how far it had 
cracked, which surprised me as it was pretty much the entire loom.









Off the car and stripped down showing cracks and missing insulation.

First Off a warning!

This is will take you the better part of a day. It requires that you pull pins out of the ECU wiring harness as well as other connector. If you are not prepared to do this, pay someone else to.
If you do want to proceed then I would say its essential you have pin removal VAG part number 401-517-02 (VAS1978/7) it cost £35.01 and can be purchased at any VAG dealership.










FYI the harness replaces wires from the coil pack all the way to the ECU plus a connector next to the battery, the oil level sensor connector on the sump, and the speed sensor connector.

This requires the removal of a whole bunch of stuff to get to it all. I removed the battery, all of the battery tray, the Air filter box, windscreen wipers and the rain tray at the bottom of the screen, also the engine under tray will need to come off, so that you can access to the oil level sensor.

Once you get all of that stuff off start removing the harness from the top of the valve cover.
The Earth ring terminal is held on with a 10mm bolt and to remove the connectors just press down on the plastic lock tab and pull back.
Just follow the wires . . . Disconnect the speed vehicle sensor connector which is on top of the gearbox and the Oil Level sensor connector which is under the sump.

When disconnecting the oil sensor connector there are a couple of things to observe. 
1. The connector has to run between the gearbox and transfer box which is tight also there's a spring clip to hold the wire.
2. In order to get the new connector back between the gearbox a transfer box I ran a bit of wire connected to the old connector, to act as a drag line.
If you forget its not the end of the world, its just a pain to get it back down the hole but not impossible.

By this point you've un-clipped the wires round to the Secondary Air Valve on side of the cylinder head.
The next part requires you to get those wires passed the SAV and the water inlet flange and towards the point where the loom joins the main bulk of the wiring system.
I've read that you should remove the SAV and water flange, however in practice you can get the loom past these without removing them.

At this point you should turn your attention to the large connector under the battery tray 
This is where you need to use the VAG 401-517-02 (vas1978/7) tool and a small screwdriver
First separate the two connectors and by looking into the end of the connector slide the pink locking block to the side. It doesn't move very much but will make a click sound.
Now using the tool push over pin 2 so that the blade of the pin goes between the tools pins and into the top and bottom holes of the connector block.
Now that the tool is inserted pull the wire from the back and the pin should come out.
Repeat for pins 3,11 and 12.
Pin 7 also needs to be removed. I found two iPhone SIM card removal tools were perfect or paper clip ends pushed into he locking pin holes worked well too.

Now that your at the battery tray side of the car you will see a black plastic square section bit of trunking that runs up the engine bay fire wall towards windscreen.
Pull the top of this off and you'll see the mail loom in it and a big connector with One wire going into it.
Disconnect it.
Running up-to the ECU you will see two connectors you want the smaller of the two.
On the side is a grey locking tab.. pull it out until it stops the connector will rise out of the ECU
There are purple clips on both sides of the connector you must remove to get everything out and one purple plastic strip in the connector that releases the bundle of smaller wires in rubber seal
The pin locations are numbered on the connectors. 
However the little raised numbers are hard to read especially on the white connector.
Each wire on the replacement harness is numbered to correspond with the location number on the connector.

To remove the pins use a dress makers pin to hold the locking tab whilst pulling the pin out of the block

The contacts that need to removed are 95,95,102,103 with the needle or pin and contact 121 which is in the main connector can be removed with two paper clip ends.

Now you can either just cut out the visible portion of the old harness and just bundle the replacement one with the old one or you can do it the hard way and unwrap the entire harness and pull the wires out.
The VW technical sheet states the first option and to be honest I think its the easier way to do it, and your less likely to damage anything else.

Fitting of the replacement wiring loom

Start at the Coil Packs and work your way to the ECU.

Its mainly following the same route as the old loom and connecting the coil packs and sensors up as you go. Pins are just pushed into place so no special tools are needed.

Be mindful that the little contacts that go to the ECU are small and although relatively tough if you don't take care they can be damaged.

When the loom is installed either use tie wraps or loom tape to secure it to the main engine harness, avoid making 90 degree sharp bends in the loom this weakens the wire and will cause damage to the coverings.

Once you have the car back together turn the ignition on, but don't start the car for about a minute this will give time for the throttle body to reset.


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## scottishloveknot (Feb 8, 2009)

you where lucky my wiring loom went on fire after a coil pack fail!!


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## Matt B (Apr 8, 2007)

Good write up but you don't need to spend 35 quid on that tool. Hammer out paper clips flat and Dremel to the desired size.
That's how we did mine

Ooo, just looked up phaar drive, what's the difference with the updated harness?


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## westcoTT (Aug 30, 2009)

Matt B said:


> Good write up but you don't need to spend 35 quid on that tool. Hammer out paper clips flat and Dremel to the desired size.
> That's how we did mine


Thanks Matt

I`ll confess to mashing one of the pins up the first time and got the tool just to get the rest out


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## westcoTT (Aug 30, 2009)

The spec of the wire is aerospace, with the whole thing covered in high temp heat shrink tubing
Its a lot lighter than the original, about half?? and half the size.

whats also cool is all the connectors and pins are OEM spec so its plug and play


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## Matt B (Apr 8, 2007)

westcoTT said:


> Matt B said:
> 
> 
> > Good write up but you don't need to spend 35 quid on that tool. Hammer out paper clips flat and Dremel to the desired size.
> ...


Its a shame i didnt see that before -It's not a job I would want to do again. Myself and lee did it one day and it wasn't fun lol.

It's amazing how much these harnesses get damaged.


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## Kprincess (Aug 19, 2012)

Do these split wires cause any issues other than being split?.


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## Skeee (Jun 9, 2009)

westcoTT said:


> ...................................Also I had had issues with the car sounding if it was running on 3 cylinders on start up, although it was an intermittent fault and only did it on cold days................................................................................................
> .


Really! You missed this bit didn't you Kal? :roll:

Also re the alternatives to the £35 tool, the pin release tool (I'll dig out the generic name in a minute) a large needle (careful you don't puncture cables with the point) or paper clip, or similar can be used to hold down the metal tang that locks the contact in place.
However it's much easier with the tool if the connector you are working on is difficult to access.

_Edit- the tool may be a 'Molex' but I'll have to have a good look under the bonnet tomorrow to see if I recognise it._

Found this on 'net:-


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## Kprincess (Aug 19, 2012)

Skeee said:


> westcoTT said:
> 
> 
> > ...................................Also I had had issues with the car sounding if it was running on 3 cylinders on start up, although it was an intermittent fault and only did it on cold days................................................................................................
> ...


I did miss it skeee, should have gone to spec savers :lol:

Looks like a new loom is in order. 

Even the chap on the video is having trouble :lol: so what chance do novices have ?.


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## Skeee (Jun 9, 2009)

I googled Molex Insertion Tool to find a picture and found this:- :lol:

View attachment 2


Note I haven't used the actual tools below Nor I am recommending the fleabay links as I haven't used the tools listed below but if you decide that it would be too fiddly to use a paperclip/needle then have a good look at the OEM Audi tool and compare to Molex release tools on ebay. :roll:

http://www.ebay.co.uk/sch/i.html?_from= ... ol&_sop=15
http://www.ebay.co.uk/itm/EXTRACTION-TO ... 35c32514af
This type of two pronged tool may also work.
View attachment 1


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## Skeee (Jun 9, 2009)

westcoTT said:


> ..............................First Off a warning!
> This will take you the better part of a day. It requires that you pull pins out of the ECU wiring harness as well as other connectors. If you are not prepared to do this, pay someone else to.....................................................


Hey Kal, did you read this bit?
And this is from some one who obviously knows what they are doing and also bought the right tools!


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## Kprincess (Aug 19, 2012)

Skeee said:


> westcoTT said:
> 
> 
> > ..............................First Off a warning!
> ...


Lol yes :roll:

Wonder what it would cost to do the job properly without damaging anything in the process?.
Is it cheaper to set it a light :lol:

Oops I shouldn't say that


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## westcoTT (Aug 30, 2009)

Kprincess said:


> Skeee said:
> 
> 
> > westcoTT said:
> ...


Kprincess! yes you did say that PMSl

Somebody like APS, Awesome, TTshop etc would do the job in about 2 hours. TBH I would do it again its not that bad a job to do.


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## Kprincess (Aug 19, 2012)

Way too far away from me unfortunately.

With all the luck I've had last year, would've been easier :lol:

Kal


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## Skeee (Jun 9, 2009)

Cheer up Kal! 

There must be an "Auto Electrician" someone who fit's high end Car Alarm/Immobilisers etc who would probably do this job quite easily.
Have a ring around, and just ask for the labour cost and how long it approximately takes.
You can then add on the cost of the Loom for a total price.

Alternatively,
Fit one of these:- :lol:


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## Kprincess (Aug 19, 2012)

Skeee said:


> Cheer up Kal!
> 
> There must be an "Auto Electrician" someone who fit's high end Car Alarm/Immobilisers etc who would probably do this job quite easily.
> Have a ring around, and just ask for the labour cost and how long it approximately takes.
> ...


I will call around and see I anyone is competent enough to do this.
How much does the loom cost?.

Yes I think that fire extinguisher is well recommended thanks 

Thanks again

Kal


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## Skeee (Jun 9, 2009)

I don't know as I haven't done this.

But are you sitting down with a stiff drink! http://www.autops.co.uk/product.asp?productid=311207 

You could PM Westcott for a better idea!

I s'pose if you considered it "Under Bonnet Bling" then that's probably peanuts!


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## Kprincess (Aug 19, 2012)

Skeee said:


> I don't know as I haven't done this.
> 
> But are you sitting down with a stiff drink! http://www.autops.co.uk/product.asp?productid=311207
> 
> ...


Frikin heck  that's extortionate for a few pieces of wire and plastic plugs.

Let the beech burn I say :lol:

Thanks

Kal


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## westcoTT (Aug 30, 2009)

It is expensive-ish, but for me there are some key benefits.
I know that it will never fail like the original one and for my perticular set up the engine electronics will be in a modular system.

So coil packs oil and speed sensors on one loom injectors on another all linked together on a Aim-tech ecu or mega spark sort of set up.

I can find out about a group buy for those interested


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## Skeee (Jun 9, 2009)

I don't know how common a problem this is for the TT but it will only get worse as many are running cars for longer, especially the TT, so a group buy would definitely be worth investigating. Especially as it's such an important loom. If I was still in my old job I would have asked for your old loom as a template and made a few as a test. I haven't looked too closely at mine yet, however as it's a lot newer than some on here and is kept indoors a lot I hopefully won't need one myself for quite a few years. If you haven't disposed of the old loom already I would ask that you keep it as it may be of great help to an auto electrician, for others. Unfortunately I don't have access to the tooling nor test facilities any more to make these. Re- the pricing, it is expensive but you need to bear in mind you're paying for the expertise/tooling etc and the guarantee that it will be made and tested to a good standard. Also this does appear to be at the higher end of the market for quality.


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## westcoTT (Aug 30, 2009)

Ive got most of the old loom, should anybody need to know a specific detail.

Kal I`ve sent you a PM.


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## Kprincess (Aug 19, 2012)

westcoTT said:


> Ive got most of the old loom, should anybody need to know a specific detail.
> 
> Kal I`ve sent you a PM.


Thank you and replied


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## Matt B (Apr 8, 2007)

Just so you know the OEM harness is about 28 quid.

Can't get over that other thing!


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## Kprincess (Aug 19, 2012)

Matt B said:


> Just so you know the OEM harness is about 28 quid.
> 
> Can't get over that other thing!


Wow  really 

Thanks

Kal


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## Skeee (Jun 9, 2009)

Matt B said:


> Just so you know the OEM harness is about 28 quid.
> 
> Can't get over that other thing!


 I wasn't expecting that. 

Do you have a part number please? :wink:

This may be correct;- http://www.ecstuning.com/ES7679/
1J0971658L

More info here, but have cut the existing loom so a different approach:- http://forums.vwvortex.com/showthread.php?4502394


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## Kprincess (Aug 19, 2012)

Skeee said:


> Matt B said:
> 
> 
> > Just so you know the OEM harness is about 28 quid.
> ...


Skeee after ordering a set of seimans deka 630 injectors from the US there is no way in hell I will be doing that again as the feckers UK customs and excise screw you for another £48 even though the injectors were very fair priced unlike the ones in the UK hint hint :!:

What a joke we have to pay for all this and more :x

Kind regards

Kal


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## searay368 (Mar 14, 2020)

Good Afternoon, Sorry for my somewhat silly request.I really could use some help with the replacement of the coil wiring harness on my 05 audi tt 1.8t roadster. I am having trouble finding the correct connector to pin wire 2,3 and 7. The car will run if i ground wire 7, however the speed odometer does not work. the harness i have does not have new Oil level sensor connector only speed sensor. What does the connector under the battery tray look like. i know i need to pin 2,3 and 7 however i cant find the correct connector. Mechanical issues and trouble shooting i am very good, however electrical issues are not my strong suit, still trying to find a diagram also. any help will be appreciated. feel free to Email me [email protected].


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