Have you cleared the fault code from the computer? It will continue to indicate the fault until it is cleared. Check the owners manual to find out how to clear the code. For most vehicles it involves turning off power to the computer for several seconds.
Your O2 sensor is a "part that is designed to wear out". there is no standard on replacing them, but if your car is running fine, and your check engine light comes on, and stays on, it's probably an O2 sensor.
oxygen sensor
Might be the sensor, each fan has its own relay
There is another problem. see related questions.
On a 1989, the speedometer signal comes from the sensor in the housing where the passenger side axle shaft goes in the transmission.
first the sensor bar uses infared tec when a different infared signal comes in the sensor bar's it turns white because the infared signal is changed video camms can do this or it wants to look good for the camera What does the first answer even say?
unbolt the sensor when you pull it out you will see how it comes apart unbolt the sensor when you pull it out you will see how it comes apart unbolt the sensor when you pull it out you will see how it comes apart
that depends on the vehicle, but usually it is inside the tank beside the pickup tube. if the tank was just replaced it is more likely the wire that comes from the sensor wasn't connected.
Yes; it comes with a sensor bar which is usually placed above the TV.
possibly the water pump
If the same code resets, then you have a wiring problem.
The speedometer signal comes from the rear axle abs sensor. The PCM has nothing to do with it. You need to check the wiring from the rear axle to the abs computer.