2nd Gen Non-Engine/Transmission Electrical problem preventing inspection sticker

[rickhans]

I have a failure that has to be fixed to get an inspection sticker by next week. The problems all occur simultaneously as follows:

While driving, usually after being in motion from . 1 to 10 miles, depending on how rough the road is:

1. The brake light and ABS light comes on

2. The speedometer goes erratic, bouncing around randomly. The faster I go, the wider the swing of the needle. Will bounce around between 50 and 70 when going 70 (using GPS to determine true speed).

3. The cruise control fluctuates in sync with the odometer movement. i. e. The needle drops, kicks in the accellerator, backs off when needle bounces back to 70.



Having changed out the ABS sensor on the rear axle a couple of years ago, and before realizing a connection between this and the speedometer, I replaced the sensor again, but nothing changed.



Where is there a harness connector that would contain these sets of wires that is probably loose and bouncing around? I plan to get under the truck and jiggle wires with the key on and see if I can recreate the problem, but would be faster if someone has solved this problem before.



One other side note, last week when in Amarillo during the snow and ice storm, I drove for a while then parked over night and had ice hanging from under the truck. Leaving the city, I drove about 100 miles or so before the problem showed up again. It was after I was in a warmer area above freezing. I am guessing the loose wires got frozen in ice and were not moving until the ice melted.



Any one know about this problem?



'98 24V 4x4 5 speed 4 door short bed 2500 Ram with goose neck hitch and ABS only on the rear, 111,000 miles.

 

[Missouri Mule]

Have you checked the vehicle speed sensor and its connector/wires?

On a 98 it should be located on the Differential (top).

 

[EdK]

I second replacing the speed sensor over the rear diff.

Ed

 

[FourBarR]

Been there with that problem. check the wire harness at the left rear wheel where it passes over the frame. chafed thru at that point. hope this helps.

 

[rickhans]

When you say the "speed sensor", are you referring to the ABS control module that sits right on top of the differential, is sort of T shaped, uses one bolt to hold it in place? The wires attach in a cap on top of the module. I have not heard of a speed sensor but have replaced the ABS contol module, as the parts houses call it, twice.



I will also check the left rear wheel as suggested. I figured I probably am not the first to have this happen. Prior to this problem, I had the rear hubs replaced because some of the bolts broke and tore up the bearing assembly. I think this was from towing too much weight on the rear axle, although it handled well and did not indicate too much weight. I was wondering if there could be a connection between that work and this problem.



Thanks.

 

[ACoyle]

Try removing the instrument pod. It's easy to do. Then look at the connector that it plugs into. There was a TSB about that time about that connector.



My '99 used to get a similar problem. While driving, I would deliver a good thump to the instrument cluster and it would straighten out for a while. Don't hit it hard enouh to crack the plastic face.



Hope thid helps.

AC

 

[Alphacowboy]

CHECK YOUR FRONT WHEEL BEARINGS! If you have 4wheel ABS, I bet one of the sensors is shot on the front hub unit. What happens is the bearing wears out, and causes the clearance between the ABS sensor and the tone ring inside the hub. It then grinds off the end of the sensor. I had the exact same issues as you are mentioning with my 1/2 ton a while back. After replacing the rear wheel sensor and not fixing it, i pulled my right front wheel hub sensor, the entire end of the sensor was gone.

 

[rickhans]

AlphaCowboy, how did the damaged sensor cause the speedometer and cruise control to malfunction? I thought about the possibility of a damaged sensor in the rear, since I only have rear ABS, but did not think it could affect the other two. I hope to be able to get under the truck today and look at the wiring. Thanks.

 

[ScottLewis]

From my reading, I think the speed sensor does control speedometer fuction and probably cruise as well since that is speed related. My '98 12 valve had a sensor on the tailshaft of the transmission as well. Both feed into the PCM and coordinate with the engine speed sensor.

Loose or chafed wiring would be my first thought because of the intermittant problem. Resistance checks of the the sensors should reveal faulty parts.



Dan

 

[Alphacowboy]

if you dont have 4wheel abs, you wont have the front sensors. On a 4wheel ABS truck, the PCM reads from all wheel sensors for speed, and ABS control. if the sensor fails, it throws off the system causing the speedo to bounce all over. Also, it can trigger the ABS at random times as well. If you dont have 4wheel abs, again, you wont have the front sensors.



I JUST REMEMBERED SOMTHING THOUGH... . You mentioned that the rear had "grenaded" and you had to have the hub bearing replaced, did any metal chunks make it into the center section?? I later had an issue with my 1/2 ton when the limited slip grenaded, it lodged a chunk of metal in the exact right spot to damage a few teeth on the tone ring that is attached to the ring gear. You might want to pull the diff cover and inspect the tone ring for chipped, missing or worn down teeth. THe more I think about it, this is what caused the issues you are talking about more than when the front ABS sensor failed. (caused similar issues but not like you described) Check the tone ring, maybe you damaged a spider gear in the differential and it damaged your tone ring. I drove around for a month with a trashed limited slip on my CTD before I figured out why my tires chirped when taking very tight corners. turned out I blew up a spider gear in the center section and there where pieces sitting in the bottom of the diff. Luckly none of those pieces found there way into the gear train!

 

[rickhans]

Thanks for the additional info. I will concentrate on the back end of the truck to find the cause of the problem.

 

[Missouri Mule]

I thought in 98 that they put the vehicle speed sensor on the differential, if you have only one component with wires going to it on the differential I would look at the tranfer case for vehicle speed sensor.

Check out your speedometer also, my Freightliner speedometer would bounce (also show wrong speed) around finally had it replaced.