Why is this 1999 ford Taurus 3.0 both downstream Oxygen sensors indicating rich All 4 sensors are new and not swapped HELP?

Answer 1

There are more sensors that feed information to the EC ( engine control)computer to regulate the gas mixture. The engine tenperature sensor is an important one. It may be telling the computer the engine is cold. Do some sensor testing work. The computer can be defective. You have to play detective with a volt-ohm meter. You either learn how to find the problem or pay the price to someone who knows how to locate that problem.

Bear in mind the sensors are just a device that reports *data* that it reads. Replacing a sensor is never going to fix the cause of the data triggering the check engine light codes (unless it is specifically about *failing sensors*.)

In addition to the above counsel, search on the code numbers retrieved from the onboard computer (OBD-II).

Then search Taurus + those codes numbers