VADSLRAM

I have a 99 2500. 99% stock.
A couple of years back the ABS and brake light came on and the speedo started acting up. So I changed the pumpkin speed sensor and the brake pedal switch. The switch because I took the first one off and I guess once it's off it will never adjust correctly again.
Well last month both lights came on again. This time the speedo is rock solid, no fluctuations at all. I replaced the switch because I figured it could be that. No luck. I did notice when I went to look at the switch there was some weeping at the hydro boost seal. So I replaced that and bled the system, No effect on the lights.
I guess I'll try to replace the speed sensor even though there aren't any other symptoms, but I hate to just throw parts at a problem.
Is there another thing in the system that could be the issue? What other components , besides the ABS module , are in the ABS error profile?
Does anyone have a schematic on the brake system?

pind

Your truck is 21 model years old, have you looked at the wiring and plug for the rear axle speed sensor? On my 01, i used to get the lights in extremely cold weather,until the diff oil warmed up enough to stop fooling the sensor. How does the tone ring look in the diff? Is the fluid clean? Any debris on the sensor magnet? Don't I just have all the questions...

vince767200

1998 Dodge Ram 2500 4X4 ABS and Brake Lite on, Speedometer bounces/intermittent/sticking

1) replaced the Vehicle Speed Sensor(VSS) on the rear differential - No help
2) Check the CAN-BUS wire loom , approximately 12" from the VSS, found one of the 2 wires broke in half with the frayed ends touching making contact while vehicle not moving.
Stripped and soldered wire together and wrapped tightly with lots of black electricians tape.
******* Good Fix*********

jda51

Had this problem on my 2000 2500 4x4. Turned out to be the unit with two hydraulic solenoids by the ABS module.