Pedal Travel Switch - ABS DIY Fix

[BorHor]

A week or 2 ago the ABS light started coming on. My dad searched around and found out that the Pedal Travel Switch/ Sensor was the problem. He found that the solder broke inside it. The fix is simple and easy.



This is what he Wrote:


The pedal travel switch is nothing more then a slide switch. When the break pedal is pressed down, the switch inside the sensor moves to a different resistor. The resistors are in series as the break pedal is pressed down; therefore, resistance increases, but it becomes open when the break pedal is pressed all the way down.

To test the sensor connect a ohm meter at the output of the sensor, and press the break pedal and you should see the resistance start to change according to this chart.


Problem I found on my PTS is that it was intermittent at the connection point from connection pins to the PCB inside the unit. My ABS light will come on only sometimes, so the failure agreed with what I found.

When troubleshooting the unit make sure you wiggle the connector to see if the resistance reading changes from some resistance to open. If that is the case you have a cold solder joint at the connection pins and the PCB.
To repair the unit, you need an ohm meter, soldering iron, solder, x-acto knife, RTV, and a small screw driver.

The way to open up the unit is to start from the back where the connector is. Cut through the sealant with a x-acto knife slowly between the body of the unit and the connector pin unit. You might need to hear the save a little to soften up the glue / RTV then use a screwdriver to pry it open.

When I opened my unit the PBC was separated from the connector. If the solder is still holding them together it will be a bit tougher to pull the PCB away from the body. When you get it open pull the PCB and switch out slowly because there is a loaded spring inside.

Inspect all the solder. What I did was clean up all the solder jints to the resisters with solder wich and resolderd them in. Solder the PCB to the connector pins and install the PCB, spring, and connector unto to the housing. Make sure you put them back the way it came out. Apply some RTV to the connector unit and push it back into the housing.








If you have any questions please ask and I will answer if I can or I will forward them to my dad.

It has been about a month and no problems as of yet.

[Horndog]

Wow, extremely detailed/helpful.

Do you (or your dad) know anyone in SJ area that will read ABS codes for reasonable $$ ??

My ABS light comes on/stays on, I'm researching possible places to start troubleshooting but figure diagnostic code might help point the way.

[BorHor]

Nope we do not know anyone that can read the codes sorry.

[matt325]

Nice write up! I have an intermittent ABS light that I have traced to the pedal travel sensor. I was about to just buy a new one, when I came across your post.

What condition does the car need to be in read the 249 ohms? I unplugged the connector and put my fluke across the two pins of the PTS just as shown in your first image, but I get no reading. The ABS light isn't on (like I said, its intermittent) at this point, so I would expect to get something. Pushing the pedal didn't make a difference. If the PTS was all out bad, I would think the ABS light would be on all the time.

Also, how do you get the PTS out? I can see a circlip and a small tab at the top. Is there a trick? I hate breaking things and then seeing how it was supposed to work!

Thanks,
Matt

[BorHor]

I don't remember there being any special trick to pulling it out.

[Pomfritten]

Thanks alot for the write up... My vert comes with the ABS light sometimes, so it's probably the same fault

[kunzs M3]

when my abs light comes on so does my asc light does this happen to anyone else

[BorHor]

^ yup

[cabrit]

great detailed info i`ve hade that problem since i bought the car prvious owner took the bulbs from the cluster to hide it about to try it ou see if it works for me
thanks alot i have aquestion for you though sometimes my asc and abs light come on sometimes it does not but when it comes on it stays on until i turn off the car and when i start it over it goes off and then comes on fter a couple of minutes of driving and sometimes it goes without coming on. was your problem similar to mine or i`m in adiffernt ball game
thanks

[kunzs M3]

thats the exact same way mine is ill be fixing it in the morning

[ChrisCC]

sorry to be a bit dumb here, but by abs light do you mean the red light next to the Handbrake light (Red P) on the cluster. I have this light flickering intermitently, depending on the road conditions...

[cabrit]

i followed your diy and come to find out i had exactly the same problem but as i am taking it apart i broke the housing a little bit i tried to glue it but now when it builds pressure there is a leak coming out somewhere or may be it could be the seal. its not much but just enough to hear depressurize when i turn the car off and when its done the brake are dumb hard until i restart it and pump it a little bit then the full pressure comes back.the housing is so brittle.
any feedback would be great

thanks

[busterhax]

how much is a new unit roughly? i have the same problem..abs light comes on after 5-10 mins of driving. hopefully this is my problem..seems like an easy fix

[tsgrady]

Here is the part #34331182594. It will run you over $100. What you are hearing is the loss of vacuum assist from the master cylinder. To answer Matt325's question: Yes, it is held in by the circlip - lift the circlip and it will slide right out.

[cabrit]

i fixed my vacuum leak but now have another problem let me know if you guys experience this after driving for a while the brakes stiff up and my abs and asc light come on
would this be a sign of a bad travel sensor or abs pump seems like it builds the pressure but cant hold it and theres no vacuum leak
any feedback will be great

[JETninja]

OMG! I need to check this out. My ABS light comes on almost everyday and then stays on till I turn off the car. Sometime if comes on with-in 5 mins of starting out, other times after 30mins or more. I've cleaned all the sensors looking for a clue. Gonna give this a try....

Also, quick question...does this part only come into affect when you using the brake pedal? My light comes on anytime, brake on or not.....

[Spin]

How hard is it to get to the pedal travel switch?

Edit;Lol,ive just seen the first picture

[frank358fr]

thanks

[Sigbigdig]

THANK YOU!!!!! Fixed my ABS thanks to you. Had been hunting intermittent light for weeks - I had swapped out nearly every component - I replaced a known bad wheel sensor - but this part never tested bad - until I jiggled the pins and read your article - Anyway, thanks for posting this!!!

[gvr4 1510]

I was going to take it apart anyway, but this gave me a lot more confidence. You saved me $150!!! Thanks!

[OppLock1]

How do you take the swtich out??!?? i really dont want to break anything... pictures anyone? please? haha

[y2kcal]

I took it out but couldn't twist it open; almost broke the wire connector part. Any advice?

[EastBayBimmer]

I took it out but couldn't twist it open; almost broke the wire connector part. Any advice?

I am stuck here too. Mine seems pretty brittle..

[y2kcal]

i pushed the pin in and out several times after trying to open it up and resolder but no luck, and then i put the thing back in place. so far i have driven the car for like 1000 miles without the asc/abs light. people may want to try this before opening it up or replacing it...

[Adijax]

I dont have that switch on my 328ic 96. WTF where is mine.