buddy's having a braking problem on his 04 fx4. says every now an then when he brakes, they brake as normal then they'll kinda rock back an forth an get hard an then the truck will keep going as if the brakes werent being pushed, luckily it's been when he's almost stopped when its happened. happened twice in the last week or so, any ideas on what it can be so he doesn't get into an accident? says his abs light comes on every now an then but that's just the speed sensor not plugged in all the way from when he changed his upper control arms last weekend, or that it's bad. could that he causing it or is it something else? thanks in advance guys

 

That's crazy. I would test every ABS sensor at all four corners, and then check the master cylinder.

 

If he just did his control arms he might have a brake line trying to collapse.

 

you think? how would we go about testing that? we did it at my uncles mechanic shop with my cousin who runs it

 

all of them? you don't think it would be that specific sensor that we might have tugged on alittle? ran the code machine on it an only code for speed sensor came up on that side no other codes