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

I have continuity between both so I’m a little stumped.

I’ll
OBDII: Heated oxygen sensor (HO2S) 2, bank 1, heater control - circuit malfunction

Volkswagen: HO2S Heater Performance Bank 1 Sensor 2

Volkswagen: HO2S Heater Control Circuit Bank 1 Sensor 2

 

No the fault stays the same always on bank 1 sensor 2 (DTC’s for bank 2 show as it’s not coded out yet) when swapped around.

I’ve had issues on previous engine where if they are the wrong way round the car will back fire and really not run very well. This is just running painfully rich.

 

Clutching at straws, but would the exhuast its self need to be grouneded also? It should be grounded through the downpipe fixings and back through the block....

 

The polo 9n3 I've got for my boy was bought with engine light on for lambda, replaced it, and would be fine for few days then throw codes up again (sorry, cant remember which ones) even started to misfire on one trip, bogging down like was too rich.
Common on them for loom to break internally between gearbox and chassis, even when metered it out, didn't show up easily, we stripped it and replaced wiring from lambda plugs to inner wing, and all has been well since.

 

I haven’t got a picture on me but the loom is totally stripped as part of the conversion with everything exposed. The ecu is sitting in the passengers footwell and the lambdas are coming in straight through a hole through the firewall. I thought where I had coiled the wiring around to tidy it up that could be causing some induction interference but alas no.

all pins seem to bell out without any resistance pin to pin. Everything looks nice and fresh with no severed cables at all on that run. The secondary lambdas have been removed from the loom (and yes it’s definitely the secondary’s that’s have been removed haha) so it’s very simple to trace them all back!

frustrating problem!

 

Attached. The loom is in perfect condition. Each pin of both lambdas gets back to the ecu plug with no issues.

Exhaust is grounded fine. Just checked that also.

 

Hi Everyone, I have T3 Syncro with the 1.8T 20v AUM motor in, its running pretty well but still needs to have the Oxygen sensors wired....
Can I please have a pinout for the 4-pin connector tot he ecu, this is what I have:
Pin 1: Blue/Red
Pin 2: Grey/Yellow
Pin 3: Grey/White
Pin 4: Grey/Orange

 

Confirmed as a faulty ECU. I managed to swap it out with another ecu to test and it trims fine. Will update once I have a diagnosis from the guys doing the software.

 

Hello I'm swaping my mk2 into tdi pd I need to plug in the brake and clutch switch ?

My brakes work with mk2 wiring
Thank

 

Hey again. I have question with T14a/8 pin. In my case I have a wire connection on 8 pin. I'm not really sure, where I need this pin conect?

 

Och, yes, I see thats pin is emty, thanks.

Today, I first time try to start engine. First I'm disconecting fuel system lines, just wiring loom full T6 brown, t10h blue and some pins from t14a (I think that enough for the first start.) Ignition is working, starter spins the engine, but fuel pump doesin't work ( I'm not hear noise from her (fuel pump I install brand new)). As I saw with tester in the pump conection, when ignition is off, pump get ~1.8 v, but when I turn on ignition or starting engine, pump get 8.8v and still is not working !
I try wire it pump stright from the battery and pump works fine ! I tryed change the fuel pump relay (I have 80 and 167), but no differents.
My battery is slightly discharged (~ 12.65v) but I don't think this is a problem ..

Sorry for my bad English.

 

I'm using golf mk2 CE2 fusebox. This car original came with 1.6 carb engine. Fuel tank and loom I using from mk3 GTi, it's plug and play to the mk2 fusebox.

EDIT: I found a problem ! Today, after work I check all wire and etc, and I found, that I not conected 1 of 2 ground wire from ECU, hes hiding behind the ECU. Now works fine !