Hey everyone,

I have a 2002 3.0 2WD. I just replaced the brake rotors due to them being warped. I also replaced the pads and bearings of course. During my installation, the brake fluid reservoir overflowed some due to me compressing the calipers (I never bleed them, only compress them). Also, I sucked some of the old brake fluid out of the reservoir to replace with newer fluid (DOT 3) but didn't suck all fluid out as I didn't want to get air in the system.

Anyways, after this was all said and done I went for a drive. Immediately after moving 10 feet from my parked position the ABS light turned on (no physical signs of ABS actually engaging). I tried resetting the battery but the light still came back on next time I drove. Also cleared the code with a scan tool and it came back right away.

The code it's giving me is C1939 - brake pressure switch input circuit failure. It's definitely related to the job I just did. However, I'm not sure if it was caused my the fluid overflow, rotor replacement, or fluid replacement.

Any ideas on where to start? Thanks!

 

Did you ever get this fixed ? I’m having exact same issue

 

Still haven't figured it out, all I know is it's some sort of wiring malfunction. I may just end up taking this one to a mechanic. I've tried bleeding the whole brake system, including ABS.

What caused yours? Did you spill fluid or did it happen after a rotor replacement?

 

I’m clueless. I’m guessing it has something to do with the rings on the rotor that the wheel sensor reads but they look ok. I’m having a fit with this.

 

What rotors did you use? I went with the NAPA Premium ones on my 2002 3.0. I had the same suspicion but wrote it off because it looked okay.

 

I used rotors from Amazon but they had good reviews and nobody had any problems with them so idk

 

Not sure if you figured it out but it's the rotors. Finally got around to putting some OE one's on and the code went away.

 

I did the same and code went away. I have been meaning to reply that I fixed my issue. Thank you for replying back

 

Where did you get OE rotors? My daughters truck has a weird issue where every once in a while while driving the brake will go all the way to the floor and not engage the brakes. When you let it back up then it will work. I just pull the codes and I see I have the same code that you had for the brake pressure switch input. I’m at a loss for what could be causing my breaking issue, but I also did brakes and rotors not too long ago.

 

I had saved the OE ones from when I originally replaced them. You could simply pull some at a junktard or a FB Marketplace parts truck. My brother has a '94 Ranger and he used AutoZone rotors without issue.

However, replacing my rotors with OE hasn't solved the soft braking, I've kind of given up on that part. All it did was clear the code.

 

I just bought the motorcraft ones online