I tackled this coil pack wiring harness problem using these posts:
Help. 1.8t B6 Coil Pack Harness - OEM Replacement.
OEM / Usp Motorsports Coil Harness - Installed [pictures]
Volkswagen Technical Bulletin - 97-04-02 vw.tb.97-04-02.pdf
A4 Mods: ECU Removal
I read these posts and they were EXTREMELY helpful, but some things were lacking, mainly pictures. Hopefully, this will make it a whole lot easier.
The full coil pack wiring harness from the ECU to the COIL PACKS is cheaper than the shorter coil pack connection made from the back of the engine.
Inexpensive wiring harness (<$75) = 8 hours of work
Expensive wiring harness (>$200) = 1-2 hours of work
Oh, well, I got the wiring harness from Euro Parts for $65. So, I went with a reliable connection all the way back to the ECU.
Be forewarned. You won't be able to remove the OLD coil pack wiring harness since it is integrated with the main wiring harness. You'll end up having to cap some wires like you would with a house electrical wiring. (See pictures at the end.)
If you want something cleaner, use the shortened wiring harness.
TOOLS:
- 1J0971658L Coil Pack Wiring Harness ($65)
- 16mm socket plus ratchet
- Crescent wrench
- Flathead screwdriver
- T-30 Torx socket or bit
- Dremel with disc (reinforced, better)
- 90 degree angled pick
- Box cutter
- Lisle 56500 Terminal Tool ($10)
- Electrical Tape
- Electrical Butts
- Wire Crimper
- Wire Stripper
- Electrical tape
- Electrical caps
- Zip ties
- 18 gauge wire
- Ring connector
- Magnifying glass. (To read the wire numbers on the connector)
- Multimeter (optional) to check the continuity of your old coil pack from PIN 3 of each coil pack to the ECU
1) Remove rain tray and rubber gasket
Disconnect NEGATIVE battery terminal
Remove driver's side wiper.
-Pry off black plastic cap with flathead screwdriver
-Use 16mm socket to remove nut
-Wiggle and pull on the wiper til it comes off
2) Remove ECU plastic cover
-Remove (5) T-30 Torx screws with socket or bit
-One is directly below the driver's wiper, which is why you removed it.
-There's a metal clip near the fender which needs to be removed or it will go flying off.
-Once all the screws are removed
-Pull up on the back off the cover first to clear the ECU and the wiring. It takes quite a bit of force and finagling to get it off.
3) Remove ECU
-Remove black metal bracket by using a flathead screwdriver and pushing down and tilting it to clear the lock
-Repeat on the other side. Should just come off though.
-Use a Dremel with a disc to cut slots into the security bolts
-I used an impact driver with a flathead bit to remove the security bolts which are secured with LOCTITE. (It came out easily with the impact driver but you can use a large flathead screwdriver.)
-Pull the ECU out from the metal sleeve
4) Remove the left BLACK connector by pulling on the Pi-shaped prongs.
-Pull off the connector from the back of the ECU
Use the 90 degree angled pick to pull on the purple locks on either end of the female side of the BLACK connector.
Once the purple locks are removed, you can pull the WHITE (TOP) and BLACK (BOTTOM) connectors from the back of the housing.
5) Prepping the NEW coil pack harness: Refer to the Volkswagen Technical Bulletin above.
-CUT OFF the SPEED SENSOR 40mm from the Y (POINT A). Cut wires, Pull insulation past wire strands, Fold wire back on itself, Tape it.
-Save the Metallic Cover for later to use as a heat shield for the NEW COIL PACK WIRES at the Valve Cover (You don't have to, that's what I did.)
-POINT B: Cut off the connectors from the 3 wires (#2 - Black/White; #3 - White/Blue; #7 - BROWN (GROUND). Pull insulation past wire strands on #2 and #3, Fold wire back on itself, Tape it.
-Save the BROWN #7 wire to ground it later near the bottom of the battery.
-CUT OFF the black plug from the Purple / Black wire. This will be connected to the THICK RED / GREEN wire you removed from the ECU with the Terminal Tool
6) Route the NEW coil pack wiring harness starting from the COIL PACKS leading back to the ECU.
7) Punch a hole through the rubber grommet where the original harness enters with a box cutter.
-Push through the ends of the NEW wires through that opening.
8) DEPIN the THICK RED/GREEN WIRE #121 from the LARGE BLACK CONNECTOR using the Lisle Terminal Tool. Push in from the female side and pull the wire out from the back.
- My NEW #121 wire was BLACK w/PURPLE stripe. Plug it into the back.
WHITE CONNECTOR - ORIGINAL WIRES:
TOP ROW:
106 - WHITE
107 - YELLOW
108 - BLACK
109 - ***EMPTY***
110 - ***EMPTY***
111 - ***EMPTY***
112 - ***EMPTY***
113 - ***EMPTY***
BOTTOM ROW:
98 - WHITE w/BLACK stripe
99 - BROWN w/GREEN stripe
100 - ***EMPTY***
101 - GRAY w/BLUE stripe
**102 - GRAY NEW (PURPLE w/BLACK stripe)
**103 - GRAY w/BLACK stripe NEW (BROWN w/BLACK stripe)
104 - YELLOW w/WHITE stripe
105 - BROWN w/BLACK stripe
BLACK CONNECTOR - ORIGINAL WIRES:
TOP ROW:
90 - ***EMPTY***
91 - ***EMPTY***
92 - ***EMPTY***
93 - ***EMPTY***
**94 - BROWN w/BLACK stripe NEW (PURPLE w/BLACK stripe)
**95 - GRAY w/BROWN stripe NEW (BLACK w/LIGHT GREEN stripe)
96 - BLACK w/GREEN stripe
97 - GRAY w/GREEN stripe
BOTTOM ROW:
82 - GRAY
83 - GREEN w/PURPLE stripe
84 - PURPLE w/YELLOW stripe
85 - BLACK w/RED stripe
86 - GREEN w/GRAY stripe
87 - ***EMPTY***
88 - GRAY w/PURPLE stripe
89 - BROWN w/BLUE stripe
I listed these as you would see them plugged into the ECU, which is upside down.
It's REALLY difficult to see the numbers unless you have a magnifying glass. If the colors are the same on yours then it should be a lot easier.
The NEW wires may be different on yours.
9) DEPIN from the THIN WHITE CONNECTOR #102 (GRAY) and #103 (GRAY w/BLACK stripe) using the 90 degree angled pick (as shown) and pull out.
-Insert the new wires into their respective slots
10) DEPIN from the THIN BLACK CONNECTOR #94 (BROWN w/BLACK stripe) and #95 (GRAY w/BROWN stripe)
-Insert the new wires into their respective slots
11) Plug the WHITE CONNECTOR into the TOP SLOT.
12) Plug the BLACK CONNECTOR into the BOTTOM SLOT.
13) Make sure the CONNECTORS are fully seated and the pins are oriented correctly. PIN #121 was tilted as were the middle wires when I installed it. You have to press the wires from the back to push the PINS forward. Once you have the PURPLE LOCKS put in place it should be properly seated.
13) Snap the back cover onto the LARGE BLACK CONNECTOR you just reassembled. ZIP TIE IT like you found it.
14) Seat the connector. Lock it in. Slip the ECU back into the metal sleeve. Put the two screws back in.
15) Cover with tape the ends of the OLD Coil Pack triggers. You could cut them. They're dead. I just taped them.
16) Connect with electrical butts (2) and a piece of wire the OLD #121 THICK wire (RED w/GREEN stripe) to the THICK BLACK w/PURPLE stripe wire that you just cut off the fat plastic connector. The RED/GREEN wire had CONSTANT POSITIVE 12 VOLT POWER. (IT WAS NOT SWITCHED as other posts indicated.) This wire needed to be connected. Otherwise, the car would not start! Tuck the wires neatly so they don't stick out when you replace the plastic ECU cover.
-REPLACE the metal bracket that goes over the ECU
-REPLACE the black plastic ECU cover. Screw the (5) T-30 Torx screws back on.
The red/green wire at the ECU and leading to the coilpacks are still constant +12V, not switchable.
17) Connect an electrical butt and a piece of wire from the #7 BROWN wire and lead it to the GROUND connector located next to the NEGATIVE side of the battery. You can crimp a ring to the end of the wire and attach it to the GROUND Post.
POINT OF NO RETURN
18) Cut the OLD COIL PACK HARNESS at a point near the back of the engine. Don't cut it too much. You'll need to cap the (4) RED / GREEN wires because those are CONSTANT and still ON! I capped them with electrical caps. and taped it and secured it with Zip ties to the main wiring harness.
19) Plug in the NEW COIL PACK harness into the COIL PACKS. Ground the harness to the valve cover.
20) RECONNECT the NEGATIVE battery cable.
After disconnecting the battery, your remote may not work properly, nor will your windows
Key in door. Hold lock button for 5-10 seconds.
Key in ignition. Turn to accessory position. Hold lock button for 5-10 seconds.
Windows:
Push down and hold. Pull up and hold. Repeat for each window. One touch should work now.
21) START your car. Enjoy!
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Originally Posted by cleoo
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