I have a 99 Ram 2500 gas pickup with the check engine light on. Also showing is the ABS light and the BRAKE light. Everything seems to work OK except the speedometer-odometer which only works when the vehicle speed gets to approximately 45 MPH. Can anyone give me an idea what is wrong? I haven't been to a shop yet. Thanks

 

Not a mechanic here, but when the ABS and Brake lights come on at the same time it may be the speed sensor in the rear differential.

 

I agree. Replace the rear wheel speed sensor. Usually fixes the problem.

 

After you replace the Rear Wheel Speed Sensor, you will probably have to find out what caused the CEL to fire. This sensor doesn't set that.

 

Thank you very much. I will try that. Don

 

Thanks for the help. I located the speed sensor on top of the differential.. It doesn't look like a difficult thing to replace, is there something extending inside the differential? Any special tools required? thanks, Don

 

Don, don't know if you have a posi rear diff or not, but if you pull that sensor and find that it's actually broken, the clutch plates in the rear end may be coming apart. I know this because I'm going through it right now myself!

 

Had exactly the same problem as you. 99 RAM 1500. Speed sensor in the rear axle went bad and speedometer wouldn't kick in until about 45. The mechanic explained that the sensor is actually a pair of magnets (one fixed, the other rotates past it, much like a magneto) and one of them had simply grown weak. He replaced the sensor and all has been well since. Good luck.

 

The rear speed sensor with clear the ABS/Brake Light/ Speedo issue but the check engine light is a completly seperate issuse. It seems like every ram get this problem. At least there will be a few less warning lights on.

 

all of the above is good information. also something to know.... you can put your instrument cluster through a sort of self test by holding the trip meter reset in while turning the ignition switch to 'on', and continue to hold the reset in until CHEC appears in the odometer reading. (anywhere from 3-10 secs). it will self test for awhile, and then put the gauges through a sequence where it drops them to 0, then about 1/4, then 1/2, then full. this will prove the gauge itself is working or not.

my speedometer intermittently quit working, but no brake light on. it would usually work ok when cold, and usually not work after sitting in the hot sun. Then sometimes it would not work for awhile, and then decide to go back to working. When not working, it would always fail to register in the gauge self test. i bought an instrument cluster on ebay for $25 (yes 25) and replaced it. fixed problem.