ABS/PARKING Brake Light

I have a 1999 Dodge Ram 4WD 1500. The ABS and Brake light on the dash will not go out. There doesn't appear to be anything wrong with the brakes. I have checked the front and rear brakes and both are good. The brake fluid
is full. I do not see any leaks. Why would both lights remain on? I even checked the switch under the parking brake to ensure it was not stuck. Any suggestions?
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There should be a sensor located on top of the differential that might be the problem. JMTCW
wrote:

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wrote:

Take it for a ride and watch the speedo at low speeds. If it doesn't show anything till you get over 15-20 mph, then what Joe said - the speed sensor on the rear differential is gone. Cost me about $41 and 15 minutes to change one a few weeks ago.
Greg
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The ABS and Parking brake lights come on when you start the truck and never go off. Replaced the speed sensor and that did nothing. The lights are still on and the Brakes are fine. Any other suggestions?
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If the lights never go out, that indicates a more serious problem - the ABS computer failed one (or more) of it's self-tests. Could be air in the lines - low fluid level - or an electronics problem somewhere. Other than the low fluid level (which I really doubt is the issue here), there's not much you can do yourself. You need someone with the proper electronic diagnostic equipment to look at it. Unfortunately, that usually means a trip to the dealership, as few independent shops have any equipment to talk to the Chrysler ABS system.
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A bad speed sensor doesn't cause the lights to come on until there's movement.
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I didn't mention but it only has the rear wheel ABS. I replaced the speed sensor today and nothing changed. I also noticed today that my speedometer doesn't move until I reach about twenty miles an hour and it seems OK after that. I also drops back to zero upon deceleration around twenty. Could this be connected?
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Yep. Which speed sensor did you replace? IIRC, there is one at the transmission and one on top of the rear, at least it is that way on the 97. The RWAL uses the one on the rear axle.
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There's an output speed sensor on the transmission, but in '99, the speedometer signal comes from the ABS computer (either 4W or RWAL systems), which in turn comes from the RWSS. The transmission sensor wouldn't affect the speedometer.
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I understand that Tom. I was wondering if he replaced the transmission speed sensor instead of the one on the rear axle.
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I only replaced the one on the transmission not relizing that there was one on the rear as well. I'm not sure how that comes out though. It doesn't look like it screws in.
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there's a bolt holding the braket for the brake line that runs over the sensor on top of the housing. take the nut off move the line's bracket out of the way. and remove the rest of the bolt. the sensor simply slides out.

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That is the wrong one. The one on the rear controls both the speedometer and supplies information to the ABS system. There is a single bolt and bracket that holds it down. Remove the bracket and it pulls straight out. Replace that sensor and your problems should disappear.
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wrote:

And it's probably going to be tough to get out. I spent most of the time replacing mine looking for the "hidden screw" holding it in. Finally, lots of elbow grease and twisting got it out. The new one slid in real easy.
They've also re-engineered the way it connects to the wiring harness. With mine ('98), there was an extra pigtail that allowed the sensor to be inserted into the axle "backwards" and the pigtail was needed to extend the wires to the original plug.
Greg
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Are you sure about that? There are 3 error codes that deal with the speed sensor(s). Error code 6 deals with erratic readings while rolling and would only trip the light when moving but error codes 9 and 10 deal with expected resistance in the sensor wiring (including the sensor) and I would think that they would trip the light regardless of motion.
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Pretty sure... a buddy and I spent the better part of the day troubleshooting his ABS problem. He would get an ABS light shortly after rolling. We disconnected each combination of two sensors (leaving only one connected at a time), to try and use the speedometer to detect a bad sensor. Each time, the ABS lights would go out after the self-test, but come back on when he started rolling (because only one sensor was showing voltage pulses). Now, it's possible that if a sensor failed in such a way as to short closed, that would immediately trip the warning lights - I don't know, we never shorted his connectors.
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Tom Lawrence wrote:

Is there a possibility for the connector(s) to the sensor to cause the problems?
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Tom Lawrence wrote:

Is there a possibility for the connector(s) to the sensor to cause the problems?
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definitely
also the wiring harness for about 18" back from the connector

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Thanks everyone for the help. I replaced the rear sensor today and my speedometer works and the ABS and Brake light went out.
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