The speedometer and odometer measure the speed and the distance driven. They are electronic components that read a series of electronic pulses that have been converted via the vehicle’s computer into readable data such as the speed. The pulses are delivered through a rotation sensor in the transmission that calculates the driveshaft’s average rotational speed. The sensors are a set of magnets that deliver a pulse.
When a Dodge Ram 1500 speedometer is not registering speed, there are a few possible causes. Here are some tips for locating the problem.
You may be saying, “My speedometer is not registering speed, but everything else is working.” If so, it could be that your fuse has blown.
- Check the fuse to the speedometer
- Replace it with another 15amp fuse
- Make sure that you fill the spare 15amp fuse slot or the problem will not go away, and the missing fuse may cause other malfunctions to occur
“My Dodge Ram 1500 speedometer stopped working, and my ABS light, check engine light and brake light indicators are all on.”
There are a few things that could be wrong here, but generally, this scenario involves either the ABS or the speed sensor. All of these indicators are tied together. Sometimes the speedometer needle will “bounce” when the vehicle is stopped, indicating an issue with the ABS system rather than the speedometer itself.
Your ABS controller or module may be the culprit. The controller is the easiest to test first. Sometimes water or condensation gets inside the controller and stops it from working. Disconnect the negative battery cable, and check the unit for water. It is located behind the battery, and also check the plug behind the battery. These two places seem to collect the condensation that will put all the warning lights on and stop the speedometer. Blow the water out with an air hose and allow it to dry before reassembling.
If you need to change the Controller Antilock Brake (CAB), here are the steps:
- Remove the negative battery cable
- Release the connector locking handle on the CAB and remove the connector
- Remove the CAB
- Install the new CAB in the housing
- Bolt it back on and connect it to the wiring
- Use the connector locking handle to connect it
- Reattach negative battery cable
If you need to change the Hydraulic Control Unit (HCU), here are the steps:
- Disconnect the ABS harness from the HCU
- Disconnect the harness on the HCU
- Disconnect the brake lines to the front brakes
- Remove the HCU from the fender panel and the valve from the engine compartment. Cover the valve to keep dirt out of the lines
- Unbolt the controller
- Install new HCU and mount it
- Tighten the bolts, and reconnect the ABS harness to the HCU and the CAB
- Reconnect the brake lines, tighten and then fill and bleed
In some cases, the problem comes from a bad speed sensor. This sensor triggers ABS and speed malfunctions. It is directly wired to the ABS and located in the rear differential housing. Check the wires for any type of damage before proceeding to replace the speed sensor. It may be a case of worn or damaged wires between the two parts. Sometimes wiring gets tiny holes in it from debris that allows moisture inside.
In order to change the speed sensor, here are the steps:
- Park flat and disconnect the negative battery cable
- Remove the wheel and assembly on the sensor side
- Detach the brake line from the sensor
- Remove the speed sensor and housing from the differential
- Disconnect the sensor from the wiring housing
- Install the new sensor and reverse the instructions
These are the most common reasons that your Dodge Ram 1500 speedometer may stop working properly. They are not complicated fixes. If you disconnect your brake lines, be sure to make sure they are in proper working condition after you reassemble your truck before driving.