ABS Bypass

[Arty]

Simply put, I absolutely HATE anti lock brakes. With a passion. They've gotten me into more hairy situations than they've come close to saving me from. I learned to drive strictly without them, and I much prefer not having them at all. I'm fully aware of what they do and that they can offer better safety, but it's just not for me. So, with that said-

 

I'm thinking of bypassing my ABS system with a simple killswitch. I'm able to do it, I just want to know if I'll run into any other issues with the brakes. Has anyone else done this?

[MilesFox]

you can just simply pull the fuse. the ABS fuse is clearly labelled. The only side effect of doing so is the ABS lite will be on on the dash. reinstall the fuse to restore the ABS and kill the warning lite.

 

disabling the ABS will not compromise the brakes, and will be no less safe than a car without ABS.

 

yanking the fuse vs making a kill switch is a non-permanent way to disable the abs without modification, and will not affect the value of the car if you were to sell it.

[Numbchux]

would help to know wtf car you have :-\

[bheinen74]

depends what year car, for instance pulling fuse on my 06 caused the brake light, and the ABS light to come on, and it disables the cruise control function with those to lit up.

on a 99 outback, you can pull the fuse and not have it disable cruise.

etc.

now the ground is warming, i have put the fuse back in. In summer its fine for me, but not winter months,

[Arty]

would help to know wtf car you have :-\

 

95 outback

[Arty]

you can just simply pull the fuse. the ABS fuse is clearly labelled. The only side effect of doing so is the ABS lite will be on on the dash. reinstall the fuse to restore the ABS and kill the warning lite.

 

disabling the ABS will not compromise the brakes, and will be no less safe than a car without ABS.

 

yanking the fuse vs making a kill switch is a non-permanent way to disable the abs without modification, and will not affect the value of the car if you were to sell it.

 

depends what year car, for instance pulling fuse on my 06 caused the brake light, and the ABS light to come on, and it disables the cruise control function with those to lit up.

on a 99 outback, you can pull the fuse and not have it disable cruise.

etc.

now the ground is warming, i have put the fuse back in. In summer its fine for me, but not winter months,

 

Yeah, I'm only doing the switch because I want to not have that annoying nag light on. Also, if I do decide at some point, for whatever unknown reason, that I want to have ABS... I just flip the switch. Easy enough.

[eulogious]

Sounds like an interesting idea... What type of trans do you have? I have a 1995 legacy FSM and looking at the TCM output for the auto, and it says that for the TCU to think that the ABS is ON, it needs to see less than 1v, so that means that if you ground that pin, it will think that abs is on, and then you can "pull the fuse" and the TCU will still think it has ABS, even though I don't know if there's any advantage to that or not. Something to think about. Here's the diagram for the TCU:

 

 

I don't know what will happen if the TCU thinks the ABS is connected when it's not, but I don't think it will hurt it.

 

Here are the FSM wiring diagrams for the ABS unit itself for the 1995 lego, just because I am feeling nice

 

 

 

So I would use a DPDT switch, one circuit to disable the ABS by splicing into the power wire for the ABS light AFTER the light and grounding it and leaving the end going to the ABS Unit open effectively disabling it while leaving the light off, and the other circuit ground the TCU pin allowing the TCU to think the ABS is still working. That way one flick of a switch and the ABS is disabled, but no lights, and the TCU won't be all sad, flick it the other way and all is back to stock.

 

This of course has not been tested and is just my thoughts looking at this, and I don't even know if splicing the wire after the ABS light would work since I don't have an ABS car, but that's what I would do to start. It's a little more work, but if you are going to go through all the trouble of installing a switch, you might as well do it right! I hope this helps!

[eulogious]

Ok, scratch my first idea...

 

After thinking about this I made sense of the system, and here's what I would do.

 

It looks like in order to disable the ABS, you remove fuse FB-5 fuse 19. When you do that, the ABS unit then grounds the ABS warning light wire, turning on the warning light.

 

So I would use a combination of a DPDT switch and a 40a bosch style relay. You will want the relay to handle the "fuse pulling" since a normal "heavy duty" switch can only handle up to 10a MAX, you want something that can stand the amps, and I bet you the ABS unit fuse is more than 10amps, and even if it was 10amps I would want something that could handle more just so I know it wouldn't fail and fry something in my ABS/brake system causing a massive failure while driving So I would use nothing but a relay for that, even if you don't disable the light. When messing with the brakes, one must be very careful and overdo it on everything to make sure nothing fails. The ABS light will pull very light amps on the other hand, so using a switch for that should be fine.

 

So wire in a relay to cut the wire coming from FB-5 fuse 19, then wire in a DPDT switch:

 

Circuit 1. "Common" to relay trigger wire (ground); "on" side grounded; "off" side open.

 

Circuit 2. "Common" to ABS light; "on" side open; "off" side to ABS Unit ABS light output.

 

This way when the switch is "on", the power is cut to the ABS just like removing the fuse, and the ABS light is disabled at the same time, but when you turn it off, the ABS is enabled, and the ABS light control is returned to the ABS unit, just like stock.

 

That's what I would do. I don't think the TCU really cares about the ABS, so I wouldn't worry about that. Let me know what you think!

Edited March 6, 2010 by eulogious

[Gloyale]

Pull the fuse, and remove the bulb.

 

Done

[Arty]

Ok, scratch my first idea...

 

After thinking about this I made sense of the system, and here's what I would do.

 

It looks like in order to disable the ABS, you remove fuse FB-5 fuse 19. When you do that, the ABS unit then grounds the ABS warning light wire, turning on the warning light.

 

So I would use a combination of a DPDT switch and a 40a bosch style relay. You will want the relay to handle the "fuse pulling" since a normal "heavy duty" switch can only handle up to 10a MAX, you want something that can stand the amps, and I bet you the ABS unit fuse is more than 10amps, and even if it was 10amps I would want something that could handle more just so I know it wouldn't fail and fry something in my ABS/brake system causing a massive failure while driving So I would use nothing but a relay for that, even if you don't disable the light. When messing with the brakes, one must be very careful and overdo it on everything to make sure nothing fails. The ABS light will pull very light amps on the other hand, so using a switch for that should be fine.

 

So wire in a relay to cut the wire coming from FB-5 fuse 19, then wire in a DPDT switch:

 

Circuit 1. "Common" to relay trigger wire (ground); "on" side grounded; "off" side open.

 

Circuit 2. "Common" to ABS light; "on" side open; "off" side to ABS Unit ABS light output.

 

This way when the switch is "on", the power is cut to the ABS just like removing the fuse, and the ABS light is disabled at the same time, but when you turn it off, the ABS is enabled, and the ABS light control is returned to the ABS unit, just like stock.

 

That's what I would do. I don't think the TCU really cares about the ABS, so I wouldn't worry about that. Let me know what you think!

 

Sounds like an interesting idea... What type of trans do you have? I have a 1995 legacy FSM and looking at the TCM output for the auto, and it says that for the TCU to think that the ABS is ON, it needs to see less than 1v, so that means that if you ground that pin, it will think that abs is on, and then you can "pull the fuse" and the TCU will still think it has ABS, even though I don't know if there's any advantage to that or not. Something to think about. Here's the diagram for the TCU:

 

 

I don't know what will happen if the TCU thinks the ABS is connected when it's not, but I don't think it will hurt it.

 

Here are the FSM wiring diagrams for the ABS unit itself for the 1995 lego, just because I am feeling nice

 

 

 

So I would use a DPDT switch, one circuit to disable the ABS by splicing into the power wire for the ABS light AFTER the light and grounding it and leaving the end going to the ABS Unit open effectively disabling it while leaving the light off, and the other circuit ground the TCU pin allowing the TCU to think the ABS is still working. That way one flick of a switch and the ABS is disabled, but no lights, and the TCU won't be all sad, flick it the other way and all is back to stock.

 

This of course has not been tested and is just my thoughts looking at this, and I don't even know if splicing the wire after the ABS light would work since I don't have an ABS car, but that's what I would do to start. It's a little more work, but if you are going to go through all the trouble of installing a switch, you might as well do it right! I hope this helps!

 

 

I LIKE THIS!!!!

 

Pull the fuse, and remove the bulb.

 

Done

 

The idea behind this is so that I can do it all at the flip of a switch. I don't want to have to bend over to remove a fuse, then take a bulb out every time I want it off.

[Gloyale]

 

The idea behind this is so that I can do it all at the flip of a switch. I don't want to have to bend over to remove a fuse, then take a bulb out every time I want it off.

 

The bulb is useless. I'd just take it out entirely.

 

If you really want wire up a switch just use spades to insert wires where the fuse goes. (just install an inline fuse on the wire up to the switch)

 

 

Chances are, turning it on and off will throw a code, so the ABS light will be on every time you re-arm the ABS, until you shut off the car and restart.