Water intrusion into a connector (X309) located under the cab, beneath the driver's seat, can cause a rough idle, erratic speedometer operation, ABS Light and Check Engine Light illumination, and automatic transmission shifting problems. If needed, connector repair parts are available from Mazda dealers, and possibly some Ford dealers.Google+
Car Problem Reports
Mazda B2500 Rough Running Idle, ABS Light Illuminated, and Check Engine Light
Mazda B2500 Problem
Average Mileage: 100,400 mi (43,000 mi - 150,000 mi)
Visitor, 2000 Mazda B2500, 150,000 mi
This describes the exact problem with my truck.
Visitor, 1999 Mazda B2500, 60,000 mi
Engine Service light came on, speedometer stopped working, idle low
Visitor, 2000 Mazda B2500, 43,000 mi
Sometimes when starting it will backfire A little and the idle is extremely ruff. Turn off engine, wait 1 minute and then seems to be okay. Happens about every 4 months. Also,engine cooling indicator will not move until engine is heated up.
Replaced the TPS and still having these problems. Hope replacing this connector does the trick, these problems caused my recent smog to abort....