99' F350-ABS & Engine Light On

Check for a rear brake disc dragging.

Have codes pulled ................

Possible speedsensor

Well, it is a '99, so you can get an OBD II (On Board Diagnostics, Level 2) code reader and find out. AutoZone Parts Stores will allow you to use one of their code readers for free, and in most states, they will actually pull the codes for you and explain what the problem is.

If you wanted to buy one of these code readers, they run in a range of about $65 to about $150 for home units that are suitable for you and I. As you move up the price points, you get more features. You have to decide if you need them or not, if I was going to buy one, I think I'd spend about $90 and get a mid-range model. Of course, you could be a professional, and be interested in a scanner that runs to multiple hundreds of dollars, but I didn't get that from your quiry.

ABS and Shift Points both come from the Speed Sensor either directly or in a round-about way, so my guess is a speed sensor.

Wonky,

The pcm, speedometer, Gem, OTC, and speed control servo all get their speed reading from the ABS module. It sounds to me like you might have a signal interupt to your abs module. If you can read frequency on your DVOM then I would look for 18-22hz per mph on your dvom with the rear tires off the ground and checking the reading at the sensor (wheels turning). If that checks out fine, then I would hook a battery up at the connector of the speed sensor on the differential. Then I would hook a 1157 bulb up to pins

21 and 9 on the abs module connector. Then put your DVOM in parellel with the test lamp, and take a reading. If you dont see battery voltage then you have a poor connection in your wires somewhere, cause you are using some of it up before the lamp. That can throw your signal off a ton. There is actually a TSB having ford techs replace the pigtail to the speed sensor and then zip tying the extra to the speed sensor on the diff cause the wires were breaking inside the insulation. So give that a shot and let us know what you find out.

Ford Tech