On my 1990 4x4 Pickup 3.0 V6 the cable is mechanical. Some toys have a VSS electrical sensor that uses a reed switch and a magnet. If you have a cable then you will have to remove the instrument cluster to get the cable off the speedometer. First, unhook the cable from the point where it connects to the transmission and inspect it. Take a power drill and attach it to the cable at this point and see if the needle moves when you turn on the drill. If your speedo cable is working and your needle moves you may need to replace the plastic gear inside the rear of the transmission. If your cable is bad you will have to remove the cable from the rear of the instrument cluster, remove the e-brake and the firewall plate that holds the speedo cable and the e-brake together. All you have to do is remove the old cable and install the new one using the same location and old parts. Make sure you re-install and adjust the e-brake properly. The check engine light will indicate if your ECU is not getting vehicle speed information. The code will go away when the signal is present or you can un-hook the battery to clear all error codes. The check engine light should stay off when your cable is replaced and working properly. If you still have a check engine light you may have other codes indicating other issues. If you want make sure you have no codes or find out what your codes mean here is what you do. First, go to the passenger side of the engine compartment and look for a small grey box about 3"x1.5" about a foot behind the battery on the fender well. Open the cover and get a small piece of wire to use as a jumper. Look in the cap and orient it so it matches the holes in the diag connector. place the wire so it bridges TE1 and E1. After you have installed the jumper you can turn the key and the check engine light will flash two digit sequences one after the other for every code you have. There will be a two second pause between two digit codes. For instance the light will blink 4 quick, slight pause then 2 quick this is the speedo sensor code 42. You will find your codes in your manual, with google or just call the dealer. Good luck.