The speed sensor on your 2003 Dodge Ram is secured to the transmission and monitors the vehicle's speed. This information is then sent to your speedometer so that you know how fast you're driving. If this sensor malfunctions, you won't get an accurate reading. Sometimes, you won't get a reading at all. You will, however, get a "check-engine" light and an associated trouble code. The sensor can be reset, however, and as long as it hasn't suffered a critical failure, you will be able to tell how fast you're driving once again.
Open the hood and loosen the nut on the negative battery cable clamp with a socket wrench.
Slide the clamp off of the negative battery terminal.
Wait five minutes and reconnect the battery. This will reset the speed sensor, since it draws power from the charging system.
Open the fuse panel under the steering column by pulling down on it with your fingers.
Locate the fuse for the electronic control module, or ECU, using the fuse diagram on the underside of the fuse panel.
Pull the fuse for the ECU using the fuse pullers in the fuse panel.
Turn the ignition on but do not try to start the engine.
Wait 15 minutes, then reinsert the ECU fuse. This will reset the ECU and it will also clear all trouble codes.
