ABS/Brake light

[huntram03]

Every once in a while for no apparent reason the ABS and Brake light come on while sitting at a light or stop sign. It has been happening for a while and we (my dad and I) have been chasing it down but cant pin it. Truck is a 99 Lariame SLT 4X4 with the 5.9 maginum. We have replaced pretty much all the brake lines due to rust, and bled the entire system a few times. Also replaced the ABS/ speed sensor on top of the rear diff. Wheel cylinders, brakes, drums and rotors have all been replaced as well. He took it to a mechanic just to get a different set of eyes on it and he couldnt come up with anything either.

So now I come to yall to get a few opinions. I have the truck for the rest of the week because he has my truck down in Tenn and would like to try to get this figured out.

Any Ideas?? GO!

 

[Redtruck-VA]

If it has a font wheel sensor I'd check that.

 

[huntram03]

No front wheel sensors..

 

[Redtruck-VA]

No front wheel sensors..

Then that would indicate you don't have ABS so would point at the brake switch itself. Do you have any brake light problems? The third light is on it's own circuit, different from the other brake lights. The switch actually has three switches, 1 brake sense to PCM, 2 third light and 3 regular brake to FCM. I'm taking this from memory so you need to confirm. Good luck.

 

[huntram03]

The 3rd brake light is out I believe it just needs new bulbs, other than that lights are fine. I did do a few road tests on it the past few days.. When light braking the lights stay off unless it's a really long light then they will come on. If I break heavy they come on once I come to a stop or right before the stop. I will replace the 3rd brake lights and see what that does, then replace the switch and see what happens. Thanks for the input!

 

[MoparMagic'00]

Then that would indicate you don't have ABS so would point at the brake switch itself.

WRONG!! sorry to point it out kinda rude however you MAY still have ABS it is REAR ONLY... there are 2 sensors in a R-O ABS system and they are on the trans (or t-case) and on the top of the rear-end.. another thing people over look is that the rear end has a toner ring inside the housing... if the rear was ran low on fluid and got hot this would be one of the possible things to wear faster.. so if the toner teeth are worn down too much to make enough signal to the sensor then it wouldn't pick up a correct signal and could possibly turn on said lights... however from my research the most common sensor to go out is the one on the trans/ t-case.. Good luck and keep us posted bud.. hope this helps

 

[huntram03]

I didnt know about the one on the trans or t-case.. I will check it out. Thanks