Hello I'm new here and granted haven't probably done thorough enough research but I need your guys help. I'm pretty new to working on my cars so forgive me for not being as savvy as id like to be when describing my issues. So I bought a 1991 1.8 MK2 Golf last fall which was in working order, but it was missing the sass I was looking for in my first project car. So after winter rolls around I spotted someone near me selling 1996 mk3 2.0 8v tech everything already removed from the donor (engine code AGG). This included rear axel with brakes, subframe and steering rack, the engine with gearbox and ECU with the loom for the engine control. This loom included from the from the fusebox side the connectors with codes "F, G1 and G2", with some research found this to be pretty plug and play which is exactly what I did. I have the engine mounted and attached the said connectors, and around this time I found out that this ECU comes with immobiliser. So I took the immobiliser to this shop that specialises in this kind of work and and not too long ago I got it back. They told me that there is two ways of removing it and they did the other way and that if it didn't work I can take it back and they would do the other way aswell (and do something with emmulator or something). And this weekend attempting to start the car with the ECU and presumably all the wiring complete the engine only turns with the starter. So after this I started checking the obvious like was it getting fuel? Well, when turning the key the fuel pump didn't start, and I'm not sure if this has something to do with the immobiliser being still active? So not wanting to give up just yet I took out the fuelpump relay out and jumped power to the pump which made it power up. After that I checked the spark which was a bit more odd. Due to the ignition coil being different I got the right one for the 2 litre which I got installed. So to testing this thing the usual way of taking the plug out and grounding it to the block I only got one or two sparks for 10 seconds of cranking. Could this just be due to bad ground which I find unlikely since there is this 30cm cable running from the negative battery terminal to the block and the mating surfaces are in quite good condition. One other thing I'm not too confident is my injector power which after some studying I found to come from the fuelpump relay, so just to be sure I jumped that aswell but never heard them working like my fuelpump. Could all of this be caused due to the immobiliser being in action? And what functions does immobiliser inhibit? And to add I didn't get the original keys and other immo hardware. If this subject has been discussed on other posts I would appreciate you linking them to me. Thanks in advance.
https://www.clubgti.com/forums/index.php?threads/mk3-8v-into-mk2-1-3.291413/ Where are you based? We had our ECU de-immobilised by a company called Vagtronics. They turned it around in 2 days and it worked immediately. This was after a significant amount of time spent trying to make the immobiliser work to no avail. Lots of info in the linked thread.
Thank you for replying and the thread I will read it through today and hopefully learn something new. I am based in Finland and the company that did my work was called "elehuolto", and they specialise in car electronics but hey told me they had never done anything to this kind of ECU so that's why they weren't sure of the outcome. I am most likely going to take the ECU back and they will do their magic and later this week when I get it back it should be fine. I will update here once I get it back probably later this week.
My car never started when cranking for the first time. But being a bit inexact for the first crank I didn't have my ignition coil grounded so that could be the reason for it not starting. But what inhibits the car from starting after that? What I have studied is that the immobiliser affects the fuel pump which seems to be the case for me but are the other issues with injectors and the inconsistent spark affected aswell?
Hello, As mentioned above, the original equipment immobiliser allows the engine to start (if it can) and then shuts it off again if the immobiliser conditions aren't met, i.e. the key-mounted chip doesn't match the immobiliser box and engine Ecu. So your difficulty with starting it probably isn't concerned with the immobiliser. Another point about the engine Ecu for code AGG is that it's coded with whether the transmission attached is manual or automatic; if you're not sure which the donor car had, ask the company to check/change which it is.
Thank you for the reply and I will be sure to ask this from the shop once I get it back to them. But I got some interesting development today. I found out that my ECU wasn't getting power and this was due to my fuse box not having the relay at spot #3 "Digifant Control Unit" relay number was 30. So I quickly bought that and now my ECU gets power. This fixed the fuel pump issue so that now when I turn the key once the fuel pump turns on for 3-5 seconds and shuts off. After that I was feeling hopeful but unfortunately it did not start. After this failure I wanted to make sure I had all my contacts in the engine compartment in good order. And this I started with the round 28 pin connector to the side of the engine, and I'm not sure how good the contact is since the connector or the spinny ignition distributor next to it make this weird sound when powering up and after attempting the start. So I took the ignition distributor apart and the contact surfaces were quite rusted (probably the finnish weather and the donor car sitting outside front ended the best part of the winter). I took out the spinning thing but I broke it in the process due to being seriously stuck. All in all the metal contact surfaces were really rusted, so could I have the car running with just these ignition parts changed and the ECU finally supplied with electricity?
the post-96 ecu will stull run the car even with the hall sensor on the distributor unplugged as the main trigger comes from the crank sensor, another common one is the fuel injector power from Z/1 gets forgotten its a red wire with a big yellow spade housing
Thank you for your reply. I have the Z-1 "Injector power" plugged. But I am getting new spark distributor, the spinny thing inside, spark plugs and the wires for them later today. Hopefully that should lead me towards the first start.
if still no luck next step ideally get a vagcom port wired in then scan ecu for faults. you can also watch the ecu sensor inputs in real time, top suspect would be crank sensor to diagnose that you watch the 'engine rpm/speed' block and if it doesnt go up while cranking thats what it is
Thank you. I have the ECU taken to the shop and hopefully that should have some effect. If not I will probably check the crank sensor and just replace it. And I have been using your VAG documents for my AGG engine and have been measuring voltages in the ignition coil area and what I found was that I was getting 12v these two when I start to crank (marked in red). But the third wire (brown/blue) which in ground I cant get it to be grounded when testing it. I'm not sure if its my method of testing it with positive attached to battery positive terminal and trying to get the negative from the hall sender connector. And is this wire supposed to ground somewhere physically cause after peeling back the old crusty sock around it, this same wire only splitted off and went to the trottle valve module, coolant temp sender and to ECU pin T68/35.
Yeah thats the common sensor earth back to ECU, it doesn't have a direct path to ground in the harness so your test is normal. All you need to check is you have continuity between that pin on distributor (plus the other sensor earth pins) back to ecu pin 35
Thank you. You have been very helpful. In addition I had a look at the crank sensor which was pretty hidden behind the oilfilter. And would you believe it, it was quite mangled to a point that the copper from the wires was visible and touching. I am hopefully able to get a hold of this sensor today and have a go at it again.
