ABS Module or Brake Switch?

[stash3630]

I had been playing with my brake switch (pictured) experimenting with how it may it may not relate to the brake over throttle cutoff (it doesn’t 😆) and now I have no hill assist and yellow wrench with code u0401 related to ABS Module (pictured).

When I turn the car on I still have hill assist until I move the car a few feet. I feel like it’s a faulty brake switch because I’ve been messing with it and not the ABS Module as displayed in forscan.

Should I just order another brake switch or two? Does this sound more like the ABS module? Could it be both?

 

[D1JL]

I would also check the wheel sensors, as a failure of one could cause similar symptoms.

 

[stash3630]

I would also check the wheel sensors, as a failure of one could cause similar symptoms.

So just pull the wheels and inspect the sensors for damage? And use a voltmeter?

 

[D1JL]

Dirt and debris can build up on a sensor preventing their correct function.
Testing electronic sensors and devices sometimes requires specialized tools and knowledge to use them.
I certainly do not wish to disrespect your abilities.
Maybe you could request assistance from someone with a proper scan tool.

 

[stash3630]

Dirt and debris can build up on a sensor preventing their correct function.
Testing electronic sensors and devices sometimes requires specialized tools and knowledge to use them.
I certainly do not wish to disrespect your abilities.
Maybe you could request assistance from someone with a proper scan tool.

I went to auto zone and oreilly’s and their scan tool was less in depth in terms of diagnosis than my forscan. So does that leave me with going to the dealership?

Also, in case you were wondering, I’m not really worried about the hill assist as a feature. Just referencing it as a relevant symptom. I’m not worried about dash lights either, just curious about why it’s there.

 

[D1JL]

I am suggesting a professional style scan tool that can read sensors while the car is being driven.
Yes, the dealerships have them also other repair shops.
Or ex professional auto techs, like me.
Mine is a Snap-On however, it is no longer up to date.

 

[TyphoonFiST]

You can Buy can scan tools that Do Powertrain and ABS and SRS codes for around $75-150*

 

[stash3630]

I am suggesting a professional style scan tool that can read sensors while the car is being driven.
Yes, the dealerships have them also other repair shops.
Or ex professional auto techs, like me.
Mine is a Snap-On however, it is no longer up to date.

10-4. I’ll try and see off I can find a cool service advisor who will help me out and go from there

 

[stash3630]

I am suggesting a professional style scan tool that can read sensors while the car is being driven.
Yes, the dealerships have them also other repair shops.
Or ex professional auto techs, like me.
Mine is a Snap-On however, it is no longer up to date.

TLDR; Update: New Brake Switch fixed the issue!

Longer update for the curious or for posterity in case others come across this thread in the future: So yesterday I went to Mountune to pick up one of their radiators and while I was there I made friends with a tech who generously used his scan tool on my ST. The original code showed up, but he was also able to go deeper and see the brake switch itself in real time (it's possible I could've done this in forscan, but I don't know the platform at all).

As stated in my previous post, the code was always visible, but the wrench icon would not appear until moving the car a few feet. Same for the hill assist. I would have hill assist until moving the car a few feet. This is relevant because I had the tech activate the brake pedal on and off while the car was stationary just after starting the ignition with no wrench icon yet, but u0401 code still displayed. In this state (no wrench) you could see the brake switch turning on/off in the diagnostic tool properly; consistent with how you were interacting with the actual brake pedal manually.

I then had him move the car a few feet to get the wrench to appear. Once the wrench was displayed in the instrument panel, manipulating the brake pedal would not cause any change in the diagnostic tool, eg on/off.

Today, my spare oem brake switches showed up, I swapped one in and sure enough it's back to normal. So faulty brake switch (that for whatever reason would only illuminate the wrench icon after moving the car) was the issue.

Thanks for all the help and advice Ford Fam. See you on my next issue haha! ;o)