Now I'm going to add even more confusion to this story. I'm a Dodge specialist and a brake system specialist, but I never ran into a flashing yellow warning light. Turns out this system can turn on the red AND yellow warning lights, and it can flash the yellow one. Both will be on when there is a diagnostic fault code in the ABS Computer.
There's two things to consider when the yellow light is flashing. First, read and record the diagnostic fault codes. Those will indicate the circuit that needs further diagnosis, or the unacceptable operating condition. Hopefully there will be a code related to a missing wheel speed signal.
The yellow warning light will flash if "a vehicle speed signal parameter is faulty or missing". There should be a fault code related to that. Also, the yellow light will flash if "the axle type or tire size are not programmed properly".
There's two different ABS systems available for this truck. One is a four-wheel system, and one is rear-wheel-ABS. The easiest way to tell which you have is the four-wheel system will have a wheel speed sensor at each front wheel. The two rear wheels are modulated together on the four-wheel system.
If you get a fault code for a missing rear wheel speed signal, (this is different from an electrical circuit problem with that sensor), look for a sensor on top of the differential housing. Pull it out and check for "hair" growing on the end where the magnet sticks out. Any metallic debris that collects there will reduce the sensor's ability to generate a signal.
For future reference, the pump motor is tested when the truck reaches 15 mph. If the yellow light doesn't turn on until you reach that speed, it's the pump circuit that needs to be diagnosed.
In the '90s, most aftermarket scanners were not capable of accessing ABS Computers and reading their fault codes. I have a Chrysler DRB3 for all of my vehicles. If you need to find one, a lot of independent shops bought them because with an additional plug-in card, it will do emissions-related stuff on any brand of car sold in the U.S. Starting with '96 models. I suspect the newer aftermarket scanners today will access the ABS Computers on a 2002 model by now.
Wednesday, March 15th, 2017 AT 5:30 PM