ABS Light Question

Ok so I got the Motive adapter in today and pushed some more fluid through the lines and bled the brakes (in this order RR, LSPV, RL, FR, FL).

Took all of about 20 min to include set up and cleanup of the Motive tool. Brakes feel perfect thus far, hoping I'm in the clear

Thanks again @Andy01DblCabTacoma for the suggestion on the Motiv adapter

 

Ok so the brakes continued to sporadically (like 1-2x per day, driving it 15 miles round trip) do the same weird thing where they momentarily let off and then re-engage. I've bled the brakes twice with the motive bleeder and they continue to exhibit the same issue.

Today I just pulled the 30a ABS fuse. Left the 60a ABS fuse in place. Drove the truck about 50 miles to include some high speed sand wash romping (great fun), and the brakes didn't once act up. So I've definitively narrowed this down to an ABS issue. Where do I go from here to resolve it without just leaving the fuse out (my OCD is bothered big time by the ABS light being on).

 

Thanks for the follow up. It makes these threads 1000x more resourceful.

Can you post a pic of the orings you bought/used?

 

Ok so my post above was premature.

But I just want to thank you again for all the follow ups with great information.

 

So I bought an assorted oil filter Oring box from O'Reilly's (didn't take any pics and can't seem to find it on their website).

Sorry for some posts prematurely exclaiming I'd solved this. At this point I feel very confident that the issue isn't going to happen again if I leave the ABS fuse out. But I'd like to not have to do that.

So I may pull those front sensors once more and inspect again. Wondering if maybe some small debris may have gotten inside the ABS sensor hole (inside the knuckle). Kind of at a loss to be honest

 

Your brake pedal drop out is a typical wheel speed sensor issue. The wheel speed sensor has to almost touch the ring. You might have to clean the hole that the sensor sits in to get it to seat as far down as posible. In extreme cases the wheel bearings might have to be replaced is there is any play, the wave form generated by the reluctor ring is very weak and anything that disruptes that signal to the ABS control unit is read as that wheel isnt rolling, i.e. that brake is locked up, so the control unit cycles the solinoid and dumps brake pressure to that wheel in an attemp to get that wheel to roll again. The system is operating as designed. If you dont have a scan tool that can show you the wheel speed sensor wave form to see which sensor is dropping out, you can usually feel which front brake isnt working as the steering wheel will twitch in that direction if that makes sense. You might have to replace sensor(s)

 

Im following because soon (hopefully) I’m putting on new UCAs (long with LCAs and new coil overs) and have ABS.

When I watch videos of the UCA swap they just carefully pull the ABS bracket attached to the UCA out of the way without disconnecting it.

Are you talking about that or literally the sensor down at the brakes assembly?

 

Thank you for that explanation. That makes perfect sense when you put it that way. It feels like front driver side is the one that drops pressure. I'll pull the sensors again and inspect the holes.

To the best of my knowledge the front wheel bearings are original with 290k miles, so perhaps they do have a tidbit of slop, but nothing I've noticed driving.

Any harm in leaving the ABS just "non-functional" with the fuse removed?

 

Well I did have to take the bracket off the old upper control arms and move it out of the way. And in order to do that I had to remove the sensors from the knuckles as the wiring doesn't have enough slack in it to effectively get it out of the way to do all the fenagling you have to do to get the old upper ball joints and upper control arms out and new upper arms in. My ABS issues began the moment I did that

 

I've been driving my truck around with the ABS light on for the last 4 years. I assume it's a wheel speed sensor but I haven't dug into it much. Truck stops just fine so I haven't been too motivated to mess with it.