GTI VR6 EDL Disable Switch

 

This is a simple addition of a switch that will allow you to turn off the Electronic Differential Lock, or traction control as some call it. This modification is only for GTI- VR6 cars of 1996 and newer. It will only work with the Teves 20 GI ABS-EDL system. The Jetta GLX (1996 and up) should be the same, but it has not been tested on Jettas. If you are unsure as to which system you have, look above the rear axle beam for a proportioning valve that will be connected to the axle with a spring. If you have a proportioning valve, you will not be able to do this modification. Turning off the EDL with this modification will not affect the ABS or the electronic brake proportioning systems. This mod is courtesy of Ian F., Bob C,. and Uwe R.

Now for the small print:   
This procedure should be carried out only by individuals experienced in automotive electrical system diagnosis and repair. If you can't read a wiring diagram, find someone who can. The switch we are using requires soldering. You will need to know how to use an ohmmeter and voltmeter to identify the proper circuits. Don't attempt this if you don't fully understand what you are doing.

Summary of mod:
This procedure requires cutting a signal wire for the ABS controller and splicing into it with a switch and a 12 volt source.
Here's two links showing the circuit.
The first one shows an overview of the entire circuit and is laid out sideways for printing.
The second one shows only the portion of the circuit we're interested in. The part we're adding is highlighted.

Background:
It was found that the EDL system turns off when you step on the brake pedal. A wire from the brake light circuit goes into the ABS/EDL controller to disable EDL while the ABS remains functional.

Goals:
What we are doing here, is to fool the ABS/EDL controller into thinking the brake pedal has been depressed. But we want to do so without turning on the brake lights whenever the switch is activated, as the brake pedal switch does.

Further Small Print:
If you screw up the procedure, don't say we didn't warn you.
YOU SHOULD PERFORM THIS ENTIRE PROCEDURE WITH THE BATTERY NEGATIVE TERMINAL DISCONNECTED.
Make sure you know your radio code first.

Parts list:
  • 3 different colors of 20 or 22 gauge wire (5 feet of each color).
  • Radio Shack 275-613 (SPDT submini toggle switch). This is a 2 position 3 pole switch with a common center post. A 275-635 or larger 275-648 will work also if you can't find the first one.
  • 64-3049 male and female insulated spade connectors.
  • You will also need one uninsulated red male spade connector to plug into the fuse panel.
  • The last item(s) are a fuseholder - 270-1238 and a few (5 x 20 mm) 5 amp glass fuses to fit the holder. I don't know the PN, but Radio Shack has them.
  • Two barrel connectors
    •

    The Switch:
    After you get all your parts together, spend some time to solder 3 wires (different colors) about 5 feet long to the switch. I mounted mine in the blank to the right of the A/C pushbuttons in the console. If you need it located elsewhere, add more wire if necessary. Pop out the blank from the console with a little screwdriver (requires a little persuasion) and drill a 15/64" hole in the center of the blank. Mount the switch in the blank with the wires installed. Make a note as to which color wire is in the center terminal of the switch. Feed the end of the 3 wires into the console and retreive them from the left lower area where the console joins the dash. (One easy way to do this is to feed the wires down just inside the passenger side of the console to the front of the passenger footwell, then push them straight across through an opening there over to the driver's side footwell.) You will have to remove the lower dash cover (under the fuse panel) to fish the wires through as well as for getting to the fuse panel later. Toss the excess wire over the console for now to get it out of your way.

    Getting to the ABS/EDL Controller:
    Open the hood and remove the black cover that says "G11" or "G12" on the coolant resevoir. This may require prying it up with a screwdriver as it is fairly tight. Now you should see the bolts that hold the coolant bottle in place. First slide the alarm switch (hood switch) toward the driver's fender to get it out of the way. Also unplug the coolant level sensor from the bottle, but don't remove the hoses. Unbolt the coolant resevoir with a 10mm deep socket and push it toward the center of the engine to give you more room around the ABS hydraulic unit. Find the large connector on the driver's side of the master cylinder (ABS controller) If you have installed a chip you will know the next step. Pull the handle on the front of the connector toward the front of the car to release the connector. Lay the connector back so that you can see its face and the terminal locations. Locate pin number 12 (see illustration) but don't do anything with it just yet.

    WARNING: Do not stick anything larger than a straight pin in the connector or you will spread the terminal and cause problems later with loose connections. Don't use a test light and don't probe any yellow or red connectors with anything as they could be airbag related. Doing so with the battery connected could result in injury or death if the airbags were to deploy accidentally!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    Getting to the back of the fuse panel:
    Go back under the dash and pull the 2 clips upward that hold the fusepanel in place. These clips just pivot upward and don't actually come off. The entire fusepanel will lift up slightly and then drop down. The panel has a spool on each end that fits into a "J" shaped slot. Maneuver the fusepanel so that you can see the right rear area of it as well as possible. Refer to the picture and the diagram of the side/rear of the FP. Locate the 3 green connectors that are on the right (passenger) side near the upper middle of the FP. A small mirror will help you to see them.

    The middle of the 3 green connectors is the one we will be working with. It's pictured here, and the outermost of the 3 connectors (X connector) has been removed so we can see W. Click here to see a photo of what it'll look like when you first lower the panel.

    Locate the 2 identical black/red (black wire with a red stripe) wires that end in the same hole of the center green connector. Using the fuse panel rear view diagram, verify that this is connector W, pin 4 (W/4)    After you have verified that you have 2 black/red wires coming out of the same hole of the center green connector, carefully remove about 5 inches of the tape that covers these wires (and a few others) as they leave the fuse panel. Take your time and don't slice any of the wires

     

    The Cut:
    Now comes the worst part. Cut one of the 2 black/red wires about 2 1/2 inches from the fuse panel. You must leave enough wire sticking out of the fuse panel to strip and crimp a connector onto it.
    Don't put any connectors on yet.
    NOTE: there is NO WAY to identify which wire of the 2 to cut because they're connected together at the plug.
    So the next step will check to see if you guessed right (I was lucky). If your luck was not too good, simply reconnect the two ends of the wire with a barrel connector and cut the other wire.

    Checking your guess:
    Here is how to see if you cut the right one:
    With the ohmmeter set on the lowest scale (200 ohms or 2k maybe if its not autoranging) touch the leads of the meter together to test it. Get a jumper wire or long meter leads with alligator clips and attach one lead to the (skinned) wire half that (just cut) is NOT attached to the fuse panel anymore. With the other meter lead, probe the ABS controller connector (carefully) at pin 12 (see picture again). Do you have continuity? The meter should read zero. If it doesn't, check again that your leads are still connected. If you cannot get a reading with the ohmmeter, then you cut the wrong wire. Connect the cut halves together with a barrel connector (the wire goes to the cruise control to shut it off when you hit the brake so ensure that you have reconnected it well. Then cut the OTHER wire at about the same distance from the fuse panel and test it for connectivity using the steps above, to be sure.
    If you have continuity, then you are ready to proceed.

    Wiring the switch into the circuit:
    Follow these next steps only when you are working with the properly identified circuit.
    1. Strip the fuse panel end of the black/red wire and install a female terminal on it.
    2. Crimp it well and pull on it to test the connection.
    3. Strip the other end of the wire (if you haven't already) and install a male terminal on it. These can be connected together (not now) if you want to remove the switch and return to stock.   
    4. Now find the wire color from your new switch that is soldered to the center terminal of the switch and put a female terminal on it after routing and cutting the wire to the proper length.
    5. Connect this to the male that you previously installed on the wire going to the ABS controller (the end that was cut away from the fuse panel).   
    6. Pick either of the 2 remaining wires from the switch and put a male terminal on it.
    7. Plug it in to the fuse panel end of the black/red wire.   
    8. The fuseholder needs to be prepared by installing a male non-insulated spade connector on one end and a barrel connector on the other end.
    9. Put a fuse in it.
    10. Connect the barrel connector to the last remaining switch wire and plug in the spade connector into empty relay socket 5, pin 1 (top pin) see picture.
    11. Secure loose wires with tiewraps. Check all connections for exposed conductors and tape if necessary. Reconnect battery with ABS controller still disconnected.
    Testing the circuit:
    With a voltmeter, you should get 12v at pin 12 when pushing the brake (switch in one position), and constant 12v with the switch in the other position (don't forget to turn the key on). If only the brake pedal feeds 12v to the controller at pin 12, check your 12v source (key on) at the fuse panel and after the fuseholder. It may be necessary to find another power source. Just be sure it turns off with the key so you don't run your battery down.   It will be necessary to mark the switch "OFF" during this system test. Remember the EDL will be off when 12v is present at pin 12 of the controller. When the switch is in the "NORMAL" position, you can test pin 12 for a ground also. Be sure it is not live before you put the ohmmeter leads to it.

    Below is a logic table showing all the possible states of the switches plus what you should see at pin12.
    You'll note that when the EDL switch is ON pin12 is ALWAYS hot, except for when the key is off.
    key brake switch pin 12
    off off off 0V
    off off ON 0V
    off ON off 12V
    off ON ON 12V
    ON off off 0V
    ON off ON 12V
    ON ON off 12V
    ON ON ON 0V

    If everything checks out, disconnect battery again, and install fuse panel and ABS connector, coolant bottle, etc. previously removed.

    On the Road:
    Don't try too hard to test it as you might accelerate tranny wear. Just wait for the right conditions or smear some oil and water on a wide painted stripe and plant one wheel on it while the other is on a dry surface. Don't do a burnout, just get enough slip to activate the EDL and flip the switch when it is active. It should stop hammering instantly. You can choose to orient the switch so that up/on means EDL disabled, or means EDL activated.


    Email corrections, additions to Ian Frechette

    Portions Copyright (c) 1999 Ian Frechette
    Portions Copyright (c) 1999 Bob Callenius
    All rights reserved.
    This web page may be duplicated in its entirety as long as this copyright notice is included.
    (See the Berkeley Software license for details concerning the spirit of this license)
    Small portions of the page may be duplicated under fair use laws.

     

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