OEM MK4 management wiring => Mk1/2/3 harness install FAQ (Now with added dieselness!)

Hi guys, I need some help with my mk4 vr6 loom. I’m trying to fix it myself and learn as I go but I need some help identifying some wires on the large ecu plug. I need to know what pins 21, 28, 37, 43 and 54 go to. I’m sure I’ll have more questions as I go, thanks for the help

 

Hello everyone, Im looking everywhere but cant seem to find it in the heyes manual.golf mk4 1.8 4motion... I have a burned wire coming out the back of the 53 horn relay in the pin 1 from a black 6pin plug and what does it connect to? I have 4 wires coming from this plug
1?
2 empty
3 empty
4 thick red and brown or black
5 red/something cant remember
6 blue/brown

It looked like it should come from a fuse 20 but following the burnt wire it follows the loom to the interior of the dashboard going deep inside the loom behind the central console...

 

Hey @rubjonny im the guy a few pages back with a MK3 GTI that i swapped a 2.8L 24v from a VW Sharan AYL

1. Any ideas what is a small vaccum line for that goes in the middle of where the heater matrix coolant hoses are connected?

2. I kept the 2.0L 8V fuel pump, i see no errors when i scan but i feel there is a slight stall in lik 2000-3000 rpm in like 2-4th gear if i keep the rev between that range while cruising. Could there bee a lack of pressure/difference ?

3. I still have to leave the car on ignition for a few seconds before cranking as it will just crank and won't fire at first key turn, turning ignition on fast, back off and on again and crank right away it will fire immediately. It's like fuel pump won't run enough or at all on first ignition.

4. I just can't manage to find a vr6 cluster, still unmatched rev signal on my 4 cylinder clock, i don't know at this point what would be the best way to fix this, either go canbus display and 3d print the cover or is there a way to code the mk3 cluster signal ? As also the mpg is not being measured correctly.

5. Car is not heating well on winter, i cleaned the matrix and still the same, i had no issues on the 2.0L 8V engine, i believe i will have to add the electrical auxiliary coolant pump or find a diagram of coolant hoses if i somehow messed up coolant lines.
Car keeps super stable 88*C stays on the middle, fan works fine, it's just that it doesn't heat inside, revving above 4000rpm start to heat a bit but still not as good as it used to be.
Coolant return hose on the tank does return/flow fine as well.

 

1. Hmm, i just started tidying up the hoses/lines etc.
I realized i had removed it and i am fixing it up now, could that have been the heating related issue (if that recirculating flap was a possible cause ?)

2. I found actually a code now, which sensor is this one because i am not sure which is pre cat and which one is post cat, is the more squared connector the first (wideband ?) Or it is the one that has a flatter connector ?


3. I will check if it runs while cranking

4. Thank you, i wonder if there will be adaptations needed to be done and if there is a manual for installation ?
Also will it fix the mpg reporting on the mfa ?
And i forgot to also ask if the vehicle speed needs tweaking or not as my clock is a 220kmh one and i wonder if the cluster reports correct speed and goes beyond 220kmh or it will report lower speed due to lower kmh than the 260kmh clocks.

5. Idk tbh, the car heats to 88*C pretty fast and then stays there no matter how much i abuse it, it keeps temp stable.
I will see if i can find a coolant hose diagram online somewhere if there is one as that may be the issue (if it wasn't because of the vaccum line of the circulating flap.

6. I forgot to ask you about this one, what is it for ?, it's a small fan behind it and it makes a static noise when i turn the ignition on (like that little fan there had a damaged bearing or if it were rubbing/scratching somewhere.


7. The outside Temperature in mfa skips when you click and arrive to it's menu, is that normal as it's not wired but few posts back you told me the wires if i decide to add it, after wiring it will the menu come up and show temp or does the cluster have to be coded for it to appear ?

 

I found the coolant system diagram and i will check if there is an error or something on the coolant lines, will also add the auxilary electric water pump.
I also noticed that there is some leak on the air orientation, whether i choose to blow on the windshield, front or legs area, it will still leak on the other sides a bit as well. (An upcoming true nightmare to fix the doors of the air orientation, dash out, blower system out and at least a full day of work)

2. Is the post cat sensor the one with the flat connector (narrow band ?) like in the picture:

3. The signal seems to be supported, IIRC when i did the wiring you told me there are reports that the mpg signal is supported on the MK3 Cluster, and it works fine but it shows incorrect consumption, it shows that it's consuming way more fuel that it actually is, which if rpm signal has to do something with it, it should technically get fixed once the tach adapter is installed as you said, the calculation should get corrected. Since on idle it runs on like 780 rpm (obd live data) while Cluster shows around 1200rpm (4 Cylinder Cluster) as of now.

4. Idk why there should be a fan there for that sensor but it really is annoying as the cabin is very well isolated in general as the car is in excellent condition and on normal cruise the only thing i hear inside is that Little fan there like it was a factory machine ventilator , if there could be a mod for it i wouldn't mind replacing it, idk if it is just my unit with damaged/defective fan or something, i remember that i checked and it wasn't loose or anything, it just makes that annoying noise, it doesn't grind any wall or something on it's place, it's just the size of approximately a H4/H7 LED Bulb Fan.

5. For the Tach Adapter should this technically do the job as shipping to my country is kinda tricky:
https://www.aliexpress.com/item/100...YYtgzeBh&utparam-url=scene:search|query_from:

6. Do any of you know a link or part number for the VW Golf MK3 GTI Headlights level adjusters plastics ? (the ones inside the headlight that get crusty plastic and break... i just can't find them.
I would like to keep the original headlights as they are crystal clear and the glass never get's yellowish, it's just that i put some sponge inside the bulb cover to keep them at a level so they barely the job, without them the level of headlights will be 1 meter .

 

Gone through the whole 45 pages as I’m about to start the wiring of my auq into my mk1. My question is if I want to retain the vw style connectors, what are they called or are they just vw Audi specific and what crimp tool do I need. I currently have an amp 90033-1 for f type connections, just not sure if it’ll work in this application

 

I meant the later Audi ones. Was sought of thinking of using them where possible to join the two looms so I could separate later if necessary as they seem much better connectors. Is my train of thought correct there or am I just over complicating the whole splicing part? Ps thanks for the heads up on where to go for the early connectors etc

 

Thanks so much. The thread had been a real help so far. The engine is in on just the two mounts so have a little bit of work to do before I dive full on into the wiring. Oh and it was an auto so have to change the pedal box too for good measure

 

Hey, I've been through this thread in its entirety and it's been a great source of information, so thank you to everyone who contributed, it has helped a lot so far.
I'm in the middle of a 1.8T conversion into a K11 Micra and am currently tackling the wiring.

The engine is an AUM from a 2003 Audi TT. I believe it's a 2003 but can't be 100% because I bought the engine, loom and ECU on a pallet. The car it came from had long gone. ECU is an ME7.5.

I have the entire engine bay harness, smaller connector from the ECU, and what's left of the larger side that leads to a bunch of coloured plugs that would go into the cabin. So far I have gone through everything I can with a multimeter and noted down in a spreadsheet every pin from both ECU connectors to each plug at the other end, then each pin from those plugs back to the ECU and whichever ground/power/relay they go to as well.

What I've been struggling with reading through this thread, and some of the tables in the first post, are the names of the connectors. I can gather that T14a for example is named because it has 14 pins, but what does the 'T' mean? Does the 'a' suggest that there is a T14b somewhere else in the car?

What are the 'G' connectors? Are they for the Mk4 fuseboxes (I don't have those)? Do the G, T, N prefixes refer to a type of connector? T14a looks nothing like T6 Brown or T10h Blue.

Sorry for all the questions, I've been looking around the web for days and seen loads of discussions referring to them, but never explaining what they mean. Hope someone can shed some light on this so I can regain my sanity.

 

Right ok! T for plug seems consistent. Does that mean then that for example each of the four coilpack connectors would be referred to as T4a/b/c/d, the 6-pin throttle connector as T6"something". Sounds like I need a full wiring diagram to check, but I haven't been able to find one so far.
Do the D-shaped connectors have a specific name? I've been able to find Timer connector in reference to the pins, but nothing for the housings, only part numbers. I figured they'd have a family name like JST SM or Molex Minifit, but I only seem to get "VAG connector" in various product listings.

Thanks for your quick response by the way @rubjonny

 

Had a quick scan though g4aumauqecu.pdf which seems to be the right one for identifying connector names, though some sensors don't show a connector in the diagram, they just route directly to the ECM. I'll go through my spreadsheet properly tomorrow and connect the dots. Many thanks again!