What does a P0125 error code and rough idle mean on a 2000 Ford expedition?

Answer 1

The reading is all the same for all types of cars nowadays. It's either your car is running lean or rich. Mainly because one of your O2 sensors is probably defective, meaning giving out a bad signal. The trouble is not in your coolant sensor. If you have an OBDII reader (with freeze frame or real time reading option), look in to the voltage output of all your O2 bank sensors. Normally, it's suppose to fluctuate between .04 to .08 or sometimes, a little bit over than that. But the main thing is it's suppose to fluctuate. The fluctuation in voltage is then sent to the computer to calculate the proper mixture of your gas/air. If one of your O2 sensor is defective, it'll either just be on a steady (fixed) voltage readout. In that case, it's time to replace that particular 02 sensor in order for the computer to calculate proper mixture of gas/air and avoid the mysterious P0125 code from coming back again. Because of the bad signal that the defective 02 sensor is giving out, the computer will give a wrong calculation to compensate from the signal readout of your other sensors.