Have read thru the forums and haven't found an answer yet.

After recently having master cylinder replaced and a rear brake job my RABS (not 4 WheelABS) light is on. Occasionally, as I am driving, it will go off and stay off until the next time I start the truck. Even then sometimes it will stay off. When it does come on it will do so when the truck is first started before I have driven it at all. I have replaced the rear sensor and the problem remains.

Brake pedal is nice and firm, not mushy and does not bleed down. Master cylinder is full of fluid. Brakes have been bled and bled and bled.

Brake light itself is not on, just the ABS light

Any ideas, solutions appreciated

1997 F150 XLT, 172K, 5.4 Triton (short plugs)




Replaced the wheel speed sensor on top of the rear end today with negative results.

The master cylinder float switch appears to move freely, not sticking to the bottom at all. Master cylinder full of fluid to Max Line.

I searched thru all 494 of your posts and found nothing as far as the procedure that you refer to. Maybe I missed it somehow, I don't know.
Could you please help further?

As a side note my Cruise Control doesn't work either.

All other systems work fine. Horn, A/C, Auto Lights, Wipers, etc. No other warning lights on. Have pulled instrument cluster as I had to replace odometer gear and replaced all lights at that time. Bench tested all and all were good.

Purchased this truck (1997 F150 XLT, Trailer towing package) approx a month ago (for $2,200.00) and have corrected several issues on it so far. Alignment, new front end parts, 2 new tires, rear brake job, new master cylinder, replaced headliner with Mossy Oak headliner fabric, repaired cracked dash and re-finished it. Added Flowmaster exhaust. Replaced plugs (fortunately I have the short ones) replaced coil on number one cylinder as it was bad. Did accent paint on center wheel caps (small mod but looks good) re-charged A/C (blows nice and cold now) and installed after market radio with blue tooth for hands free calling.

Truck has straight body and good paint. Runs fantastic. Planning on Gotts Mod, new seat covers (Mossy Oak from Coverking) and some fog lights.

My last two issues are the ABS light and the Cruise. BTW, it does have a trailer brake controller.

Thanks in advance for your help.

 

I'm not sure on a '97 but I don't THINK the master cylinder has anything to do directly with ABS system. ABS basically looks for any one wheel that stops spinning (locks up) when others are spinning and if so then it takes over modulating the brakes. It also detects an open or shorted circuit on any of the wheel sensors, and it turns on ABS light if it detects any. That's basically all it does. My guess is that someone knocked something loose when changing the MC, brakes or working on the dash. Cruise control MAY use the same fuse and wiring as ABS. I don't know. Look at the list of the fuses and see if any control both ABS and CC. If they do then check that fuse CLOSELY, If you don't find anything wrong with it then start checking the wiring to and from it. FWIW it's probably easier to chase down the CC problem first and fix it and see if that also fixs ABS too. You might want to unplug the trailer brake controller until you sort this out if you suspect it. Most simply plug in.

I see that you added that you changed the rear brake sensor. (only one???) Are you SURE that the new one is good? I get a LOT of BAD, new parts these days. Manufacturers cut every corner in manufacture and then don't test their items before selling them. Grrrr! Check the sensor wirring all the way back to the ABS controller. especially the connectors!!!!! A loose or dirty connector would give you exactly the intermitant symptoms that you describe.

Get your electrical problems sorted out before modding the engine or adding other electrical items!

 

I am having a similar problem. The light came on and I had the code read. It indicated that it was coming from the rear sensor. My truck is a 2002 with 2wd.

Is there a way to trouble shoot to determine if it is the sensor as opposed to the wiring?

Thanks