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ABS light and red E-brake light have been on since purchasing my 94' Ranger 2WD, did a diagnostic test by unplugging the connector by the parking brake with the black and orange wires, then grounding the pins inside the connector, and the ABS light gave a Code 4. According to the research I've done so far, this is due to "RABS Valve Switch Closed or Open Dump Valve". As much as I'd like to address this issue, there is a ton of conflicting info out there about this illusive code and it gets really confusing. I don't even know where these valves are, what they look like, or how to fix this issue. Being able to find them would definitely be a good start lol. I know you guys on here know what you're talking about, so any help is really appreciated. Thank you.
RED brake light is not part of RABS but will cause Yellow ABS light to come on
Red light mean one of two things, parking brake pedal is down, or Brake fluid in Master is low
RABS can't work with parking brake on OR low brake fluid, lol
Parking brake pedal has a switch that will GROUND the Red brake light on dash if pedal is down(even a little, unplug that switch, see if Red brake light goes off
If Red light is OFF then the switch is the issue or pedal is not coming up enough to OPEN the switch
If Red light is still on, open the hood, on the passenger side of brake Master is a two wire Sensor, unplug it(I assume you have checked the fluid)
See if Red light is OFF
With both units unplugged Red light should be off
Now plug back in the Parking brake switch and see if Red light stays OFF, if so replace the Sensor in Master
If both lights are not OFF then my wiring diagrams are missing a wire for the 1994s, lol, which is possible
RABS code 4
If you fixed or found the reason for Red light then leave what ever was causing it unplugged
Restart and go for a Drive, ABS should reset with key off and on
See how long it takes for Yellow ABS to come back on, and how many times you used the brakes
The RABS unit is in the frame rail under drivers side of cab at the front of cab
Unnplug it and plug it back in, that cleans the connection, go for a drive again see if yellow light stays off, worth a try
The diagram shows ABS wiring, there is a reset button on the valve but very hard to press, but you can ground that wire, light blue/red stripe to reset
Also you can test OHMS for the 2 valves inside, 1.2ohms and 4ohms as shown
Unplugged the ground for the brake light, plugged it back in, its now off and only comes on when the parking brake is engaged, perfection.
Turned the truck on and went for a drive and the ABS light was still on, taunting me lol. Did the diagnosis again thinking there was another code underlying the other one but no, still code 4.
Found the RABS unit, unplugged, looked very clean and no bent pins, plugged it back in, and the ABS light was still nice and bright. Tried to attempt to hit the reset button but that thing is stiff. Grounded the lt. blue / red wire and nothing happened, ABS light was on.
Will test for OHMS once the multimeter is charged up.
In the meantime, any more ideas? 🤔
You can use an adjustable proportioning valve in its place, or just by-pass it
No, it never worked very well since there is not a lockup sensor on each rear wheel, just one sensor on the differential, so one wheel could lockup and never activate RABS system
The current valve is a proportioning valve as well as ABS, when you apply the brakes 70% goes to front wheels and 30% to the rear, cars used 60/40
Adjustable valve lets you set what works for you
No, the ABS light is control by the ABS Module in the cab
I think its above gas pedal area towards the center on the firewall, should have ABS label
Try pulling out Fuse 15 in cab fuse box, 20amp, in 1994 that fuse should just be for ABS module, so shouldn't lose anything else but the ABS light, and of course ABS system, lol
That's a good idea, I might pull the fuse if I get an improper ohm reading until I can get an adjustable valve or a relatively cheap RABS valve off of a parts truck, it already doesn't work anyways. It feels wrong but it's better than letting the ABS light win this war, lol.
Thank you for your help, I appreciate it 👍🏼 I'll update this thread when I get around to checking the resistance of the valve and what not, hopefully tomorrow when I come home
I realize this thread is over a year old, but @aidanjewell did you ever end up replacing the RABS valve? I'm also pulling code 4. My ABS light was off until I replaced the speed sensor because I had a bouncing speedometer needle problem, so I thought it must have been related to that but who knows. I feel like I've always had some weird electrical gremlins with this truck. I haven't done any ohm testing of the valve yet.
I realize this thread is over a year old, but @aidanjewell did you ever end up replacing the RABS valve? I'm also pulling code 4. My ABS light was off until I replaced the speed sensor because I had a bouncing speedometer needle problem, so I thought it must have been related to that but who knows. I feel like I've always had some weird electrical gremlins with this truck. I haven't done any ohm testing of the valve yet.
Shortly after this thread I ended up just putting some black electrical tape over the light behind the dash bezel and called it a day. Let the new owner know and sold it a few months later. Couldn’t manage to find one at a pick and pull within reasonable distance from me and I wasn’t able to fork out the money for one online at the time. I would definitely recommend OHM testing before doing anything too drastic, especially since it was off before replacing your speed sensor. But, who knows, I also had some electrical gremlins in mine, I think it’s just a perk of having an old Ranger
I gave the reseat/reset solution a shot. It's tight and there and the boot on the plug mostly hides which wires go to which pin, but it looked like the 2nd one in goes to that light blue/red wire which I grounded. It didn't seem to reset it, so I then quickly grounded each of them one by one in case I got it wrong (hopefully that doesn't mess anything up). I slathered on some dialectic grease to the pins and put the hardness back on, but it still gives me solid yellow after the quick ignition test.
Does anyone have a helpful picture or youtube video of ohm testing these 2 connections? I'm not quite sure how to read that diagram above. There are other videos that I saw, but none for the 4 pin harness like on mine.
Figured I'd post this year for the benefit of others who are clueless like me and just figuring this out (I think).
I got some alligator clips and clipped them onto the pins of the valve. I assume the two leftward pins correspond to one valve and the two rightward ones correspond to the other. The rightward ones gave me an ohm reading of 4.7 and the leftward ones seem to go off the chart. I guess that means the valve is shot.
It's getting harder and harder to find this part. Junk yards were expensive and not nearby, so it wasn't really worth it. My options were Amazon and Advance Auto. Amazon was $210, but after a 15% discount plus a $42 core refund through Advance, I picked it up $147. Not terrible with 2024 inflation. If it turns off my ABS light and improves my or my descendants chances at avoiding an accident, it's money well spent.
Hey @RonD (or @aidanjewell for that matter). I got the new part but figured before I did anything I figured I'd hook up my multimeter to the pins of the new unit to see if it looked any different than the old one, but I got the same exact readings for both pairs of pins: "1 . " for the first one and "4.7" for the other. From the manual below, it seems like if you get "1<spaces>.<space>" that means you're over the limit. Do you think I'm somehow getting the wrong reading? I can't imagine that both are defective. I really don't want to go through the trouble of swapping it out, bleeding the system and swapping it back if I'm barking up the wrong tree.
I decided to go ahead and do it and just hope that it would work.
It was more than a pain than anticipated as it is very tight in there. Thankfully I had a very short 7/16 wrench that gave me enough clearance to work. Pulling off the front driver's side wheel made it a lot easier to reach under and move the RABS around to line up the bolt hole and bolt it down with the other hand. Reattaching the brake lines almost gave me a heart attack as I couldn't get the rearmost line to stop leaking after tightening it down several times. So, I finally slid the brake line all the way into the RABS and then hand tightened the fitting, trying to not let it move while I wrenched it down the rest of the way. That way finally got it to stop leaking fluid, pumped up the brakes until I got solid pressure, topped off the master cylinder, took it for a spin and the light went off.
So, moral of the story I guess is that if you're pulling RABS code 4, even if the ohms look normal (or at least consistent with a new module), your RABS is probably bad. I'm glad to have that annoying light off and also some extra measure of braking safety.
RABS Code 4
