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

So this Brown/Black FCM wire should run into the Sharan T14a Pin 11 right ?

Will do when i drop the coolant on the evening (after work), will try the resistor first.
But now that you send the T14a diagram, where is the coolant temperature sensor ? and what is that pin4 common sensor earth ?

I tried that but the oil pressure light still kept blinking, So what about the low pressure one, where it is supposed to be or what should i do on the 24V, also here is the one that the Sharan had on the filter housing:

So it's T14a Pin 6 - Vehice Speed Sensor since you sent the diagram and where do i wire it to now ?

But now that T10/9 is the coilpack power 20A what would be the one for Sharan T14a since the pins are different.

Thanks will do.

Ok, some wire colors seem still different but since it's a sharan, the same applies as first post, the pins should be the same.

Where would i wire the Pin 9 for coilpack power (20a) ?, to something like ignition ?
11 - so this one should wire with my missing brown/black wire from FCM right ?
13 & 14 - if i keep the SAI, where would i normally wire these two ones ?
Where is the coolant temperature one so i can give it a try with the resistor first ?
2-7 i assume are for the one under the oil pan ?

 

Wow thanks, so i ended up using the hose with two pin sensor that was installed in the 2.0L 8V Radiator Hose like i previously posted (dont mind the dirty style of the connector, once i fixed everything electrical related, the wiring will be OEM+++) :

It fitted nicely on the 24V and the sensor location is very close to thermostat housing and just wired an earth to one of the pins and the other to G2/3 Yel/Red and temperature gauge is working perfect, it stays right in the middle of the bar which is 90*C, i had some air coming out of the coolant tank that got me worried first but that was just the air coming out of the system as it wasn't plummed, first thermostat opening session, it happened twice and no more air.
Then after all that calmed, i let the car running till temperature reached around 95*C, and turned off the engine as i realized the fans were not going to kick in, after checking the FCM power cable wasn't connected well, pressed it till it clicked. to make sure wiring is right, i did jump the fan thermoswitch connector on the radiator RED wire +12V into the White/Red which was Fan speed 1 Low and fans kicked in, so it was just the FCM connector, tried red 12v+ to yell/red which is fan speed 2 high, the FCM was clicking once i jumped but fan didn't run at high speed.
To make sure its not a FCM issue, i removed the fan connector and checked with a test lamp, high speed was coming to the Fan connector. Sorry TLDR
Long story short Coolant problems solved !:
- Car is working fine, no more air into cooling system.
- Fan is kicking in now at like 90-92*C at Speed 1 but Fan is defective as it's High speed isn't working so i will have to replace the FAN so i have speed 2/fast as well.
- Temperature Gauge working.
Coolant side of thing resolved, Million thanks for everything !!

Sorry for repeating this one but i asked if you know where the low and high pressure switches are located on the 24V, are they both on the filter housing or one of them is somewhere else ?
The problem is that i have to remove the front of the car to have proper sight/vision on it due to clearance issues with coolant and AC hoses covering it.
What i did is i lied under the car and managed to see the one on the top of the Filter housing on the AC Compressor side which is black and part number 06A 919 081 D and is 1.2-1.6 bar and it's black like in the picture:

Was this one supposed to be the High Pressure Oil Switch, this is the one i replaced with the white 1.8 bar one and run a wire for it so i don't have to do additional splicing of wires If this was the high pressure oil switch, where should be the low pressure oil switch located on the 24V engine ?, is it also on the filter housing next to high pressure one or somewhere else ?

Or is this one that you mention on Post #1 : the blue or brown switch 0.25-0.3bar switch part number 028919081, 028919081B or 028919081H in the spare hole supposed to be the low pressure one and i have been so dumm to not realize it even though i did read that section like 10+ times, and above all that, a T M10x1 thread to fit the oil temp as well for temperature output to MFA cluster that i do have. Wow im dumm... Sorry if this is correct that i just realized.

Thanks, i assume this is the last thing for VSS and it should work after joining these two wires.

Will give this one another shot, i hope what that person argued on facebook about same mk4 era signal is right or just vr6 clocks working would be fine but what i hope is that RPM signal isn't can bus as well on this engine... as that would complicate things a lot...

1 & 2: now that i understood these would be wired and done correctly after all.
3 - will do, is this one supposed to turn the battery red light on on the cluster to tell that the car isn't charging ?
4 - done
6 - to be done tomorrow and to be confirmed if working afterwards.
7 - ok
8 - to be done tomorrow
9 - to be done near the final stage of wiring before starting to wrap the wires back to OEM+++ style/condition.
10 - will do tomorrow
11 - done today.
12 - will run it.
13 & 14 - yes i am using SAI for now, no one knows how to SAI delete. they struggle to remove immobilizer in first place... will/might deal with that later on.
For now i will attempt to not delete anything related, i can place the SAi pump on the passenger side where AIrbox used to be as that place would remain empt anyway, so there is more than enough place to mount the SAI pump.
Afterwards after i manage to get a full ECU read/dump i might consider sending the files for online modding like SAI, CC and the usual stuff deleted then write it to ECU afterwards.

Thanks again for everything.

 

Update Post, although read previous post as well:

RPM Gauge: YESSSSSSS !!!, it is working now with my instrument cluster

Coolant Sensor: Like i shown on previous post, i solved it by using something like your 3rd method but i also plan to run two wires into the sensors on the thermostat housing while the car is warmed up to see if one of them report temperature into the gauge, if that turns out to be true then i can use that one or run two wires inline with it's connector just so maybe ECU needs that info to not throw an error or something, or find the corresponding wires to wire it to the gauge, i heard one of them is used for cold start to have a bit higher idle speed till the cars warms up?, not sure how this function is called in English (like every car idles a bit higher in rpms for a few seconds - a minute or so until it warms up a bit), doesn't happen if the car is already warm.
However i will have to remove the radiator/front panel one more time to install the two additional oil switches (low and temp), to replace the Fan as it's high/fast speed isn't working.

Oil Pressure Switch: The light now is turning off when i start the engine, i think was missing an earth or something after doing a cleanup of wires, although i haven't found yet a T M10x1 piece to install the low pressure one and the temp one.

Alternator: haven't wired it yet, but next to it's connector (green and brown) there are two extra wires that were cut a black one and a blue one, i was so dumm to wire a AC connector to it , i think those were related to the alternator as well as the AC connector is not related to/with engine wiring harness, but rather on the other half or engine harness. If that's true, where am i supposed to wire the black and the blue one ?.

VSS: i still have no speed signal, i might have fried the VSS Sensor due to the difference into T14a as its pin on the T14a was wired to a straight 12v positive from battery, i will get another one to just give it a try.
Anyway i am still a bit confused on the wiring side, especially now with the Sharan T14a diagram, i kept the old mk3 sensor and it has 3 wires:
VSS Pin 1: MK3 is black which is G1/4, where should i wire it, is it just a positive or T10 Orange Pin 6 ?
VSS Pin 2: MK3 is white/blue which is G1/11 where should i wire it T14a Pin 6 ?
VSS Pin 3: MK3 is Brown which is F/4 but where should i wire it, is it just an earth ?

AC: i found the aircon switch ready and aircon switch off wires and they have same colors as Mk3 ones however i would like to know about the AC Compressor connector, i kept the one from MK3 harness, shall i use that one without having to modify anything aside the two aircon wires being merged together ?.

Getting closer and closer to completion

 

Yes but i think there is a hole in the front side for a second one, even though there is an extra one, i still need to find that T M10x1 thread to fit the oil temp one for the MFA.

Ok thanks.

Will have to remove the front one more time for the extra hole for the oil sensor, then i will get the part numbers of the two sensors on the coolant flange.
They both have two pins only, so i assume ill have to figure out the wire colors of both and once you figure out which is the temp one, i can just use that for the dash temp gauge as well if it works fine, other than that, i already have temp reading with that extra 2 pin one on the hose near the flange or TLDR the 3rd method on your post #1.

Wow, i guess i know what they did when they removed the engine from the donor car, they cut the black and blue connector of the alternator for some reasons (most likely they couldn't remove the connector / lazy bastards) so they just cut it. the other brown and green is the AC Compressor one which they plugged into the alternator as it's the exact same connector, so i have to just remove the ac one from the alternator and splice it to the MK3 AC Comp connector.
and use that connector for the black and blue for the Alternator.

Thanks, this is what i needed. i will have to check the ignition on this one as it's clearly missing something since there is no sign to it.

Nice, i kept the old AC Connector as well but since it's already there on the engine loom but just connected accidentally to the alternator connector i will keep that one, just replace the connector to the Mk3 one so i can plug it into my Mk3 Compressor, i will keep the old wires so i can splice the one for the T14a/5.

Also a couple of updates since my last post:

RPM signal seems to work on all MK3 clusters, you will get rpm gauge working wether it is a 4 or 6 cylinder but you may want to add a note that 6 cylinder engines on 4 cylinder clusters won't show correct RPM.
On idle, my 24V stays at around 680/720 rpm (by OBD reading), but in the cluster it stays at 1100 rpm so the signal is different, at 5000 rpm in cluster, the real rpm in the engine is 3200rpm. so it goes at the redline very early on a 4 cyl cluster, i will have to swap that one.

OBD Port, was a piece of cake, as you said only that gray/white wire that was already there on the engine bay that i didn't remove after the splicing from the MK3 wiring and i can diagnose perfectly fine.

I have a couple of Errors though that i would like to know if i am missing a wire or something.

1. 17936 Camshaft Timing Control, Bank1; Open Circuit (intermitent)
2. 17924 Variable intake manifold switchover valve: open circuit (intermitent)
3. 17840 Secondary Air Injection Valve: open circuit (intermitent) (could this one be because the engine wiring already has it connected and the second half of the wiring does also have one for that ?).
4. 17457 valve camshaft control exhaust, bank 1: open circuit (intermitent).

There are some other can communication ones for abs, cluster, engine/transmission, airbag etc.

 

On the point of clusters and rpm, on the polo 9n3 the 4 cylinder cluster is identical part to the 3 cylinder, on another forum it has been said this can be altered on vcds so it reads correctly, haven't looked into it further, but is it possible ? And a possible solution for above?

 

Correct, i can 100% confirm it after comparing the RPM in the cluster and live with OBD Diagnostic.
Yes i have found a few of them, will pick the best condition/deal one.

Yes they do come back after clearing them however T14a/7 was the big problem with the most previous ones, somehow i had it as an earth instead of power.
After wiring it to ignition live, i heard more clicking sounds than before, ignition live came to VSS connector as well, the intake and exhaust cams valve/sensors errors disappeared, MAF sensor error disappeared as well.
Fired the engine and wow the engine sounds different as well, no more high fuel smells, the car somehow before sounded more like a VR6 but now it does sound like an R32, wilder sound on mid/high revs, MPG signal dropped significantly, car has much more power than before although i am getting the rev hangs, will have to wire the brake/clutch sensors to resolve that problem as well.
Didn't test the VSS yet as i got tired today and was lazy to swap the VSS sensor but since i got power to it now, i can assume the problem should be solved.

Now the only errors that i have left are these:


A. For the lambda sensors, i think i got lucky, it seems that the VW Sharan only has 2 instead of 4, i think i've seen that information on the forums there somewhere, here it is: #14 on the toyotec vr6 engine codes and outputs thread, someone mentioned there.
"AYL found in Sharan and Alhambra - 1 wideband O2 sensors, both cams equipped with hydraulic adjusters just like R32"
So i assume if it has only 1 wideband it should have 1 narrow band as well or how is it called. so the second half wiring harness won't need any tweaking since it does have only two connectors instead of four.

B. Tank ventilation valve: i assume it's the one for carbon canister ?

C. Secondary Air injection valve: Hmm could be 3 possibilites IMO but you should be able to correct me there.
1. Engine Harness does have the connector already plugged in but the second half loom (big ECU connector) wiring harness does have a SAI Valve connector as well, i assume i should get rid of one of them and that's maybe it's throwing that error ?.
2. Possible electrical damage while experimenting until you told me that Sharan T14a has different pins.
3. Another missing wire ?

As for the CAN errors i assume i can ignore them as wether they are coded out or not they shouldn't cause issues, just a cosmetic obd thing ?.
SAI and Post-Cat lamda, i will try to keep all these functions simply because i don't know any competent ECU coder in my country as of now.
However i will ask the guy who did the Immobilizer defeat if he can dump/read the ECU and put the file/image into a USB Drive and send it for online tweaking somewhere (if that is a possibility ?).

 

Had a quick look earlier, but took a bit of a search for it, seems the polo 9n in address 17 you change value of the figure 01131 to 01141 to change from 3 cylinder to 4, apologies if that's wrong description, I'm not up on technical stuff yet, but it's made my life simpler when I put the 1.8t in the polo hopefully.

 

A. For the lambdas, i just haven’t purchased them yet, as they didn’t come with the engine, the car was already broken apart and sold out, so all i took was the engine complete with it’s engine small plug harness and the ecu, fuel pump and the alternator.

I think the wideband (if its the D shaped connector one) is compatible with all the mk4 petrol era engines, a few google searches, showed the same part number from a 1.4/1.6 16V showing compatible with: sharan 2.8 v6, so i just took a used one from a scrapyard for testing, if the error clears and doesn’t come back, i can assume that im done with it.
As for the flat connector one (if its the post cat or narrow band or how we call it), the ones i have checked with part number, didn’t show any compatibility with 2.8 v6 sharan, so ill search a bit more on other scrapyards.

B. So that error won’t go away if i use the MK3 Canister right ?

C. Second option seems better and cleaner because I don’t need to touch the Engine Harness and leave it all OEM.

 

Hi, I've got a question on the check engine light (and also EPC light). I just pulled a harness from a 2004 GLI with a BDF motor (US model) and it does not have wires present at the T10w pins 8 or 10.

The only mention of these lights in the Bentley is that they are located within the J285 (Control module with indicator unit in instrument panel insert) so I'm guessing they're illuminated by signals from the CAN BUS? Smog test requirements are strict in CA so it's a must to have the check engine light functioning. Is there a way to get a trigger wire for each light, or at least the check engine?

 

O2 Sensors just connected to the plugs, still no holes drilled into the downpipe just left them outside until i drill the holes and weld their mounts into the downpipe, massive performance difference just like that without proper exhaust Oxygen measurements, it finally started spinning on idle at 2nd gear when you floor the throttle.

How does the Sharan ECU show that error: 17834 tank ventilation valve: open circuit.
Unless i missed it somewhere i don't see on post #1 which wire(s) is/are for the carbon canister on MK4/Sharan.
As the MK3 Carbon Canister simply had just a hose that went into the 2.0L 8V Intake Manifold and the 2pin connector (on the engine connection side of the things).
The black wire was wired to ignition live and the Green/Yellow wire was wired to the MK3 ECU Plug.
Where am i supposed to wire the Green/Yellow wire ?
I tried to earth it, the valve opens but the engine immediately starts to have like a hiccup/unstable idle, as soon as you remove the wire, it idles perfect.
Is that hose from the valve supposed to go to the intake manifold as it used to go on the 2.0L 8V ?. Some more clarification would be appreciated here.

MPG signal: sometimes acting weird, actually for me it's l/100km, one day it was reporting perfect, in real time, idling at 2.7-3.4 L and as i full throttle to rev limiter going to like 18.7 etc, but this correct reading is rare, most of the time the numbers are very high and kinda bugged, idk, it stays like at 39.4 you let the car idling for a while and you just see that RNG number (will show a random big static number like 30-90.x and keep going up for no reason, bugged ECU or what could possibly be, any ideas ?

Oil temp sensor: still haven't managed to find a T M10x1 thread to plug the Additional Sensors.

Alternator: I had the Sharan AC Compressor plug connected into the Alternator , used the OEM Sharan wiring for that and now alternator working perfect (as explained in your post #1)!.

Coolant temp: using the 3rd method for now, it is working perfectly fine but i expect the oem sensor to report just fine, need to figure out the wires to it, after i remove the front and send the part numbers.

Brake/Clutch sensor: wired yellow/white to ignition live, the black/red to earth and yes, no more rev hangs on gear changes.
Will run all the wires inside and install them as well but for now i just wanted to test the performance of the car.

VSS: i couldn't believe how much of a difference it will make into the engine power, it rips now

Secondary Air Injection Valve: i didn't correctly understand what you meant on previous post on how to remove the extra plug on the harness, the one from the small ECU plug (engine wiring) is connected as it was when it came with the engine, the extra one on the big plug is unused, where do i wire/cancel it.

 

John thanks for the help mate! I'm a ways off from being able to test adding wires to the pins but I'll report back here when I'm able.

 

I did a bunch more searching on this and ended up finding a CAN converter that handles the tach signal. I sent an email to the company and got an immediate reply that

"The CAN Convertor RPM has a 2nd output that could be used for a MIL light.
The output switches to ground."

I'm definitely going to try this out. Here's the link for anyone that might be interested:
https://www.vdveer-engineering.nl/en/shop/can-convertors/can-convertor-rpm-mk1-mk2-detail