All Trucks, Campers, Trailers, RV's and Motor Homes - 98 Dakota ABS

98 Dakota 4x4 3.9V6. When stopping kind of hard the other day something just didn't feel right in rear brakes and thought I heard a noise in Right rear as I came to a stop. I pulled the right rear just to check to see if I might need brakes. Pads were fine but there was evidence of a wheel cylinder leak but does not seem to be leaking now. I cleaned them up and reinstalled drum and then readjusted. Road tested and felt fine. I used the truck later on with no problem. Anyway I got up to go to work and my "Brake" light and the "ABS" light are on. (No the emergency brake is not on or "half on".) Everything seems OK stopping wise. First thing I thought was that I disturbed the sensor. It is actually mounted on the differential so no way

more info on Dakota. I can go under the hood and pull the 2 connections from the controller and turn on the key. The "brake" light is out but the "ABS" is still lit. Now if I plug everything in and turn the key on to get the two lights and then go pull the two connections the "Brake" light remains lit until I turn key off and then on again. No change in ABS just stays lit. MY service manual doesn't show any testing procedures for the ABS

If you had a leak, that switch that senses differential pressure between each of your dual brake systems may be off-center.
Getting it back to center is a bit tricky, and messy.

Check the fluid level in the Master cylinder, and the float switch for sticking.

The red brake light indicates that the hydraulic system has been compromised. You should always begin diagnosis with the red light first. Since the systems are "Interrelated" , you may find the ABS lamp is a ghost, induced by a Hydraulic problem in the main service brake system.

ABS lamp by itself = ABS system problem...ABS function disabled, conventional brakes operational

Red brake by itself = ...Aside from the obvious parking brake, or disconnected harnesses, is a failure in the hydraulic system of the service brake.

Both yellow and red together = Hydraulic problem with related symptoms to the ABS....diagnose red first....

I'm willing to bet ,that right rear wheel cylinder has been leaking for a while, and emptied you fluid reservoir.....

I did check master cylinder. It was below the "add" mark but nothing critical. Not sure if it has a float switch. It didn't empty out or anything but I filled to correct mark. I agree that the ABS itself may be OK and the switch may be off center which causes both lights. I am not losing any pedal at all so I am not sure why switch may be off center but I would like to try to center it. Not sure how to do this. I assume trying to bleed switch itself. It is pretty well accessable

FYI... I didn't realize I was in wrong forum

Been working 12 hr days. Lights are still on but haven't had time to mess with it. Finally got some free time. I feel no brake problems whatsoever. Anyway I bought new shoes, drums and wheel cylinders. I will put on tomorrow and completely bleed system and go from there. If lights are still on I have a friend who runs a garage who has the fancy Snap-on scanner that DOES read brake codes. If you're wondering why I don't do that first..I figure I got to fix that leaking cylinder sometime so....;)

replaced rear brake cylinders, shoes, and pads. Bled complete brake system. Brakes feel fine. "Brake" and "ABS" still on:wall:

As I stated I did a complete rear brake job. Well just for the heck of it I pulled the front wheels (pads are still 80-90%) and I pushed the caliber pistons back into the bore to see if maybe this would maybe have an effect. Of course it didn't. I am positive that my problem is not hydraulic (although possibly a stuck combination valve or proportioning valve). I am going to see my friend with the ABS scanner tomorrow and see if it shooting any codes.

My neighbor just came over with his Snap-On Motis. We scanned a Code 35 (Rear Wheel Sensor Open) I will replace the rear sensor tomorrow and hopefully that is it.:D

I replaced the rear sensor and started the truck and whoopie no "ABS" or "Brake" light. Well I went inside to shower, etc. Later I took a drive to my brothers a mile away. Half way there they both popped on!!. After driving a while I noticed that my speedometer now does not work until I am guessing 25 mph or so. I do not believe I had a speedo problem before.
P.S. If I shut off the truck the lights will go out and remain out until I hit that 25 mph or so. If I shut off truck and cruise around very slow the lights will not pop on although speedo stays at 0:wall:

is the wheel speed sensor completely seated in the rear end housing? The ECM gets its signal for the speedo from the wheel speed sensor. Is the sensor the right one? the problem may be in the wire between the ECM and the speed sensor, and just got worse when you moved the wire around.

:D I took your advice (along with a mechanic I know) and took a close look at the sensor with a mirror. It didn't seem to be completely seated although we are only talking a hair width. At the same time I used a continuity tester while moving the harness around in all directions. Didn't find any wire problems. I made sure the sensor was down tight and brake line clamps were put back the way they were and all connections were snapped tight. I road tested and guess what...speedo worked all through speed range and so far no lights.
The tolerance of that thing must be exact because it was hardly noticable.

The tolerance is extremly tight, the sensor is a small generator and has to be close to the trigger wheel inside the differential housing to work. Hope that fixes your troubles.