The ABS light and red amber brake light came on in my 1999 dodge dakota. also the spedometer failed to register below 45MPH. its a 5.2L automatic 4x4. The chiltons manual says you can ground out the diagnostic connector and the ABS light will flash you a code. well the book never says where that connector is located and i sure couldnt find it. supposedly it could be either tucked up in the dash to the right of the glove box, or near the parking brake release handle. there are only 16 possible codes and only 2 of them show the amber brake light being active, both of those codes point to a bad speed sensor on the rear differential.

If you have these lights come on do this:
on the top of the rear differential is a sensor, remove the connector and get your multimeter. do a resistance test on the sensor between the 2 pins. the resistance should be between 1000 - 2500 ohms. If the resistance is not within spek order a "RWAL speed sensor" NOT the speed sensor on the transmission. you can only get it from the dealer, mine was like $55

I posted this because when i originally ran the search i had to dig thru about 5 threads, none of them had a finite answer. hopefully the next guy that searches finds this and just checks the rear sensor before wasting time trying to find the damn diagnostic connector like it says in the book