Resetting the OBD-II codes on a Ford Ranger is a simple fix that requires no expensive tools. The truck's computer stores trouble codes it detects from sensors placed throughout the vehicle. When it finds a problem, a light illuminates on the instrument panel warning the driver of a problem that needs to be addressed. The vehicle's computer also stores codes for routine maintenance. For Ford Rangers that are model year 1996 and later, you can use an OBD-II scanner to read the codes. An OBD-I scanner needs to be used for vehicles 1995 and older. Once the codes have been read by the scanner and the problem fixed, you can reset the codes by disconnecting the battery.
Pop up the bonnet of the vehicle and find the negative battery cable, usually black. Use an adjustable wrench to loosen the bolt attaching the cable to the battery.
Lift up and remove the negative battery cable from the battery.
Wait one minute, then put the negative battery cable back in place and tighten the bolt.
Start the engine. Check the instrument panel to make sure all the warning lights are turned off.
You will need to reset the clock and reprogram your radio station presets, because all of this information was erased when you unplugged your battery.
Keep the positive and negative battery cables away from each other.