The most difficult part of replacing an oxygen sensor on a Ford Ranger is in the determination of whether or not the oxygen sensor has failed. The oxygen sensor is one of the only things controlled by the computer that can illuminate the check engine light for reasons other than a failure of the sensor.
It is true that the sensor will set a code for the oxygen sensor, however the code usually reads that the oxygen sensor is out of parameter or the heater element has failed. The code that indicates the heater element has failed is correct and requires replacement. The out of parameter code means that the oxygen sensor signal is not in the normal range.
If other problems are the cause of the mixture being out of range on the Ford Ranger, the sensor will indicate this to the computer. The computer has no control over the other problems so it sets a only a code for the indicator of mixture. Anything that can effect the fuel mixture can cause this. The ignition system, leaky intake manifold, PCV valve, coked intake manifold or throttle body, wrong timing, dirty air filter, wrong thermostat, leaking or clogged fuel injectors or mechanical problems with the engine. If all these are in good working condition, the oxygen sensor is probably bad. An oxygen sensor measures the oxygen content in the exhaust stream in real time. If the signal is out of range the light comes on.
You will need some basic tools to replace the oxygen sensor if it is bad. Tools such as a 7/8-inch wrench, a ½-inch drive 7/8 oxygen sensor socket with slot in it for wire, a ½-inch drive ratchet, a floor jack, jack stands and anti-seize compound.
Raise and support the Ford Ranger on jack stands. Remove the electrical connector to the oxygen sensor. Remove the sensor with the wrench or socket, whichever fits for the year truck being worked on. Install the new sensor, using some anti-seize compound on the threads. Without the anti-seize it could rust in the pipe.
Install the wiring connector and make sure it is clear of any hot heat source such as the exhaust pipes or exhaust manifold. Lower the vehicle and clear the code by removing the negative cable on the battery for ten minutes.
