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.
Rough Running Idle, Erratic Speedometer Operation, ABS Light Illuminated, Check Engine Light, and Automatic Transmission Shifting Problems on Mazda B4000
Average mileage: 142,785 (65,721–201,491)
31 people reported this problem
2001 Mazda B4000 201,491 mi, Visitor
It takes a couple of trys to crank abs light stays on rouph idling some times guits but will crank wright back up check engine light stays on sometimes don't want to shift out of low gear for a little while not fixed yet
1994 Mazda B4000 120,000 mi, Visitor
all of the above about to try to fix it