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

Discussion in 'Engines' started by rubjonny, Nov 8, 2013.

  1. rubjonny

    rubjonny Administrator Staff Member Admin

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    T6/3 is for the starter motor, you keep your original wire for that. if you meant T6/4 yes you can wire to battery or wire it like late VR6 to G2/9 at the fusebox if you're unpicking the loom anyway keeps things neater in the bay

    since you have a bit more load on t6/5 just run it to Z/1 with 10a fuse job done

    for t14a/9 any 4 terminal relay will do pretty much, the VW 53 relay is a nice common one 40a rated so plenty.

    feed the live pin from Y spade or battery live jobs a goodun. you could run both the relay and t6/4 from live with a 20a fuse if you wanted, then it'll be close to a factory mk4 24v just rather than ecu switching on the relay you have it ignition switched instead
     
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  2. A2_Eric New Member

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    Johnny did you mean G1/4 here?
    Also, T14a/7 shows as ground on my diagram?

    Also, a question on G1/8, it's a 20A fuse, is that not enough to run 2 lambdas, MAF, and leak detection pump?

    Many thanks for all your input as always!
     
  3. rubjonny

    rubjonny Administrator Staff Member Admin

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    Yes sorry I meant G1/4 isn't fused, G2/4 is fused by fuse 15 but it's only 10a so you don't want to put too much load on it (smaller amp engine electrics is ok, like actuators and such)

    G1/8 shares the fuse with the fuel pump, this is why you don't want to go crazy with it

    Which diagram are you looking at? I'm referencing Sharan which iirc was where your small ECU plug loom came from? The MK4 loom has different pinout for this plug
     
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  4. A2_Eric New Member

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    Ah, my apologies, I'm looking at the MK4 diagram so please disregard.

    Good to know on the G1/8, thanks for that!
     
  5. Sniki New Member

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    @rubjonny
    I finally finished my wiring harness and everything works fine, i used a 167 relay since it was 40a rated for the ECU permanent live + Coilpack Power.
    However i have a few before completing small problems.

    1. If car stays for a while, when you go and crank it, i need to crank it for like 5 sec (it won't fire on first crank)., i turn the key back to 0 and crank again, the second time it will fire up right away. What could the problem be, is it possible that i need a 409 fuel pump relay like @Andy947 had that issue ?.
    Was the problem similar?, once the engine starts, you don't have the issue anymore, turn it off, fire it up again and it will start no problem, the problem happens only if the car stays off for a longer period of time (haven't measured how many minutes or hours).
    Or could it be the immobilizer of the MK3 causing that issue ?

    2. The oil filter housing had a spare hole which i ended up fitting the Oil Temp Sensor, i didn't use a low pressure oil sensor at all since these engines do not have any, however when i check on the MFA, the oil temp always reports 160, is it possible that the sensor is faulty ?
     
  6. rubjonny

    rubjonny Administrator Staff Member Admin

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    1. to rule out the fuel relay, replace it with a 17/18/100 relay this will force the pump on constant with ignition. if the problem still occurs look elsewhere. I had exactly the same symptoms with a dodgy coolant temp sensor on my digifant, really odd. you can use vagcom ecu measuring blocks to check all of your sensor inputs in real time so it would be an easy catch if its that

    2. that suggests short to ground, disconnect the green/black wire and your oil temp should read 0 or ---, if so the sensor is to blame. if not, you have a short on the wire or have used the wrong wire for the oil pressure and temps, maybe try swapping them over
     
  7. Sniki New Member

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    Thanks a lot, problem is solved, relay 100 solved the problem. Car fired up in a sec.
    Removed the Green/Black wire from the sensor, oil temp on MFA shows --- now, so hopefully that means sensor is faulty, will get a new one or grab one from the scrapyard and i think that should be it.

    What i left for later though is the brake & clutch switchs.
    Should bypassing them solve the issues, am i going to miss any functionality ?.
    I have 4 spare wires from the old loom that i didn't remove for this purpose so i have no need to rerun them but instead make use of these by simply cutting them and wire them for the clutch and brake pedal switch(s).
    1. The Red/Green wire F/5 if i am not mistaken ( ECU pin 32 (8v) as the fusebox FAQ says).
    2. The Yellow/Black wire which i think is G1/10 (i have stickers on them with exact pin however...) - ECU pin 23 (4cyl), air mass meter pin 3 (8v)
    3. The Black/White wire which i think is G1/7 - ECU pin 9 (4cyl).
    4. The Red/White wire which is G1/8 - lambda probe pin 1 (post-96).

    Should i use any of the wires from the existing brake switch for taillights connector or the second one has wires run separately ?

    Also i remember we used to discuss about Outside Air Temp sensor and my car didn't have the wiring for it while MFA does have that function, i would like to add it since i have all these spare wires that i could make use of by cutting/re-wiring them to the fusebox area.
    Which pins should i use for that, as the fusebox suggests many of them and not sure which one to use, fusebox FAQ says:
    G1/2 - Brown White which i assume should be earth
    G2/2 - Red White which should be the Temp signal to MFA cluster
    am i correct ?
     
  8. rubjonny

    rubjonny Administrator Staff Member Admin

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    ok cool, try a 67/80/167 instead of a 409 see if that works better. you dont want to keep a 100 permanently as the fuel pump wont cut out in a crash

    the brake switch I dont think you would notice, but the clutch switch can cause rev hang between gears if you dont fit it. you can just drive the car and see how it is

    https://clubgti.com/forums/index.php?threads/fusebox-faq.219775/
    F/5 is starter cranking live
    G1/10 is ecu relay power
    G1/7 is ecu relay delay switch off
    G1/8 is a fuel pump relay power feed, shared by the fuel pump fuse

    For brake light switch you want plug E, use the red/black 'brake lights on' wire for the ECU black/red. Yellow/white goes direct to ECU, red/yellow is perm live which goes to the mk4 switch brown/red and the last black/blue wire is ignition live which you can take from whatever handy switched feed you have to hand this feed will also do you for the black/blue on the clutch switch as well (all this is covered in the first post)

    for outside temp yep you want G1/2 and G2/2, makes no difference which way round you wire it
     
  9. Sniki New Member

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    My MK3 had a 167 fuel pump relay already and it was causing me that issue that i mentioned previously, do you think it's possible that it was faulty ?, i have another 167 relay if that's the case which i used it for the ECU+Coilpack live feed ignition switched as you told me to do on previous posts, is 167 ok for ECU+Coilpack, or will the relay 100 do the job for that as well ?
    Can you write some relay models that would do the job for ECU+Coilpack that i did.
    Ok so i can simply bypass the clutch pedal switch like you mentioned on first post and i won't have issues with it right ?
    Are you sure that you didn't check the wrong fusebox diagram ?
    VW Golf MK3, CE2 Fusebox says what i mentioned previously, not what you just said or am i wrong ?
    Ok i will do those two switches as well since that's what is left to be done anyway.
    This should be easy, just to grab two wires somewhere outside.

    I have an additional question, what would be the best 1.8T 20V engine code/model overall to use for a MK2 or MK3 swap, i am thinking of grabbing one while i can as they used to be like nuts but the demand is constantly increasing thus the price getting higher and higher every single time.
    I also assume i won't need cluster swap as it's a 4 cylinder engine anyway.

    Also an additional idea that came to my mind is that a VW Golf MK4, 3-door with a 1.4/1.6L petrol engine is usually pretty cheap as these engines are considered crap here, they are oil burning addict engines and they have no power, the idea is that you have a newer chassis + wiring compatibility for a swap, you have AC/Climatronic, power steering and ABS all by default pretty much, so i assume it would require less work compared to a MK2/MK3.
    The only thing that im curious is what happens with ABS, will that require coding or i can simply grab the abs from the donor ?
    Just wanted to get a brief summary of the swap requirements in general.
     
  10. rubjonny

    rubjonny Administrator Staff Member Admin

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    You can use the 167 or 100 for ecu/coilpacks, just need to re-jig your wiring to suit either way. only a 67/80/167/409 type relay will work in fusebox slot 12 properly due to the terminal layout if you want the fuel pump to be triggered by the ecu. the 17/18/100 relay will just have your pump on constant with ignition from a pure wiring standpoint this is fine the engine wont care, but for safety reasons this isnt ideal as if you have a crash the pump will continue to run which could be very bad

    you can try bypassing the clutch switch, as I say worst case the revs will hang between gear changes. if it bothers you then its easy to add the switch back in later if you have at least run the wire to the fusebox area :)

    The basic terminal functions are as I say, though what they are connected to depends on the car. G1/10 if used will be power from the ECU relay in slot 3 regardless of model though. G1/7 on the TDI and pre-96 VR6 is used to actually turn on the relay (relay 109), but as you have an 8v in this case all it does is allow the ECU to keep the relay on for a few seconds (relay 30). F/5 is on the same feed as the starter motor, so the ecu knows the engine is cranking. you dont need it for your new ecu though so it can be binned entirely. G1/8 is used for the lambda probe(s) heater, its fed by fuse 18 along with the fuel pump which is why you dont want to put too much load on it

    the base engines are all very similar, dont believe all this talk of forged internals :lol: the main thing for the various types is what turbo/injectors/whatever is fitted and what ECU is used, this is what changes the power and torque figures between models more than anything else. so out of the box the BAM or the other A3/SEAT equivalent with same BHP (AMK? I forget) would give the best figures but you can achieve the same by fitting the required parts and having whatever 20v ecu you like mapped to suit. This thread covers it very well:
    https://www.clubgti.com/forums/index.php?threads/decoding-the-bam-hype.286688/


    with engine swapping in MK4 Golf, the main thing is you start with a petrol base car if you want petrol engine, and diesel if you want diesel. the internal wiring between them differs quite a lot. then there is the very early coloured plugs with green rather than white and 10 pin 'T10' plug vs later 'T14a' this is easy to work around either way, the plugs are mostly the same pinout wise just a couple pins swapped. if you fit early engine to late car you may have cluster issues. if the old engine had an oil level/temp sensor that can be turned off, but sometimes the rev counter is sent over can and some of the early ecu wont send that signal. for that either fit early clocks or try adding the rev counter wire back into the cluster harness. though having said all that unlikely you'll want to put an early engine in anyway since no-one likes to touch them any more :lol:

    the other potential is adding in DBW pedal, not 100% sure but you may need to do some welding to get that in if it doesnt have one? ABS I'm not sure on either, I'd imagine its not so bad though as you're keeping in the same era of car, again later ecu may need coding work if you have an early non-can ecu going into a later car with can abs system or vice versa also same deal if its old and you need can you might have to add that in... but I'm sure someone will chime in or make a new thread elsewhere as that stuff is out of scope for this thread
     

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