I started this swap in January 2020 as a way to learn more about VW’s and auto mechanics in general. I bought my 1991 GTI with only old pictures to go off of. It was previously ABA swapped. Once I towed it back to Texas I took the flooded engine and exhaust out and threw nearly all of it away, leaving the shell and rear suspension. A few weeks prior I had purchased a 1995 Jetta GLX for parts, which the engine came out of. It was originally OBDI so I purchased a new harness (engine to fusebox) from a VR6 Passat, keeping the main engine harness from my engine with some new sensors. I feel like people can be intimidated by wiring when doing this swap. I was too, and just got more confused the more I researched. This is for the people that really want to learn how to wire their own swap but have little experience. I hate the term ‘plug and play’ because this swap does require some modifications, but this is about as simple as it gets. These principles can carry over into Mk1 or ABA swaps also.
Some of the best advice I received since starting this swap is that the best way to really learn the wiring of your car is to sit down with your harness and the wiring diagrams. A Bentley manual and wiring diagrams helped when looking for something specific but A2resource was my best reference. Here are the links you will need, and you’ll want to print this out and take notes:
CE2 (1989+) fusebox layout: Central Electric 2
ECU pinout: Motronic Pinout
I also decided to cut out the wires I didn’t need. It made the harness look neater in my opinion and I didn’t want extra wires crowding outside my fusebox not being used. I was definitely ridiculed by my coworkers for this (sorry Matt) because I cut power wires that were spliced further down the track. This resulted in me not getting power to my MAF and I didn’t know why the car kept dying. So just be very mindful what you’re cutting! Another thing to keep in mind is if you delete something, a resistor needs to take its place (solenoid deletes). I’m not sure if having open circuit faults will prevent misfire recognition and fuel trim adjustment. I don’t know for sure if this is used with motronic systems, but I can say for sure I did not notice misfire codes until I fixed the open circuit faults.
Please know how to solder and tap wires, the connections will be much stronger and cleaner. Here is a good video:
- To go from CE1 body harness with a CE2 fusebox, you can re-pin everything to CE2 connectors if you’re good with that, or buy interior wiring. But this thread explains it better: CE2 Swap DIY (harness sources/basic components)
CE2 connector colors:
Yellow- Headlights
White- Engine
Red- Steering Column
Blue- Dash/switches/cluster
Green- Misc
Step 2: Get the CE2 fusebox diagram from a2resource and start labeling the connectors. Each one is a unique shape, color, and # of pins. You can’t mess this up, it only fits a certain way.
Note: A majority of your connectors will come from the interior harness. I only ended up with A1 (front left headlights), A2 (front right headlights), G1,G2, F, and of course the power (thick red wire - goes to a Y slot) , ground (thick brown wire - goes to Z2), and fuel injector power (red wire with yellow connector - goes to Z1). You should have a jumper on your fusebox for 30 to 30b, the fuel injector power goes above that. If you are using wipers and AC, these connectors are green.
Step 3: Two wires coming straight from the ECU you will want to put aside. First is the K-line, gray and white wire, spot 43 on ECU connection. Second is the VSS (vehicle speed sensor) wire coming from spot 65. This will tap into U1/11 (to accurately get speedometer reading for mk2 cluster)
Note: It was tricky for me to find numbers corresponding to wires on the ECU connector, there are little tiny numbers behind each row. A good reference point is the thicker brown wire in spot 1 is ground, that will be on the bottom left when you’re looking at it.
Step 4: This next part is relative to whatever you want to take out. If you find a wire that is in the way and don’t know where it goes, trace it back to the ECU connector and find the pin it goes to. Then you can see on the ECU pinout diagram what exactly it is for. Cut it or a safer option, get it out of the way if you don’t need it. Same goes for sensors. Like I mentioned before: CHECK FOR SPLICES DOWN THE TRACK BEFORE CUTTING
Ex) I found which connector went to knock sensor 1 by tracing the gray wire back to spot 34 on the ECU pinout
Step 5: Retape it back together. I used tessa cloth tape, I recommend starting with small 4 in zip ties to manage where everything goes before you tape it together and can’t see anything. And I mean dont tape it until everything is in the car working properly.
Step 6: Installing - self explanatory but I’ll add it anyway - the ECU connector will go through the hole in the rain tray (you may have to widen the hole). Also push the connectors for the MAF/knock sensor 1 and O2 sensor(s) through. I drilled a separate hole for this. Then push the fusebox connectors through the firewall (there should be a grommet), leaving the rest out in the engine bay. Connect the large round connector to the engine harness (located in a bracket behind coil pack)
Find: Making a VR6 tach signal work with a Mk2 cluster!
I haven’t tried this method yet so I can’t verify. You can try this or get the tach adapter box from S&P. (I’m not one to speak because my mk2 tach doesn’t even work)
For the mk3 cluster, I hear you’ll have to jump E/2 to D/11 or D/08 to get power to ECU.
What I did was buy the mk3 headlight harness connector for $30 on ebay and added wire. On the harness there is a yellow/gray wire for horn and brown/gray for horn ground. This wiring diagram can be found in your bentley manual (97-106) but here is a few:
Headlights:
(Left) (Right)
low - yellow/black Low - yellow
High - white/black High - white
Fog lights:
gray/yellow
Parking lights:
(Left) (Right)
gray/black gray/red
Blinkers:
(Left) (Right)
white/black green/black
For key on power, just find any wire with signal with key on (I forget which one I used
but anything you can see going to the 15 line on a wiring diagram). Then attach the
gray wire to the k-line coming from pin 43 on the ECU.
In addition to the links I added, here is a couple YouTube threads that helped me immensely:
Humble mechanic's white wookie playlist:
Jake Rawson's How to Mk2 VR6 swap:
Hope this helps!
-Jackie
