Both of the lights (yellow ABS and red "brake") stay on constantly while I'm driving. The only way I can get them to shut off is if I press on the brakes quite hard to come to a stop (they won't go away if you're in park and press down.)

I'm thinking this had something to do with a recent seafoam I did. At first I thought maybe I didn't secure the vac line tight enough to the brake booster but it's fine.

Also might note that my brakes feel no different.

 

Dumb question but... did you check the brake fluid level? The red brake indicator usually means the fluid level is low.

As for ABS- what year truck are we talking about?

 

Trust me, around me there is no dumb question because I run into a lot of problems that I think are elaborate and turn out to be something ridiculously stupid.

But no, the brake fluid is fine.

And it's a 1989 5.0 F-150

 

This is what it was on a 92 Explorer I used to own. Both lights were lit on it too. The brakes worked fine, in fact we drove it for months this way after I checked the system out. The ground cable for the battery had one of those cheap replacement ends on it. A previous owner had put it on there and I was too lazy to replace it. About every 2-3 months I was having to replace that end due to corrosion. I got tired of it after a year and purchased a correct cable from Autozone. After I got it changed those lights went out and never came back on again. It might be worth a look to see if that is your problem.

Chris

 

That would make sense since I have a crumbling neg battery cable and I have noticed some electrical problems in the past... I'll check it out.

 

If you need to replace one cable, chances are you need to replace both.

An easy way to check them is to just cut a little bit of insulation off- if the individual strands are dark, the cable is bad.