I know this has been covered extensively; however, I haven't been able to get a clear answer searching this forum or pistonheads.

I've received a P0133 code (bank 1, sensor 1 for O2 sensor) on and off for the past few years. It usually goes away with the next drive cycle—until recently. So, I'm hoping to purchase a new 02 sensor.

A few questions:
I've read to replace the sensors in pairs—is there a difference between upcycle and downcycle sensors? I believe bank 1 sensor 1 is an upcycle location. Am I correct?
I've read that there are identical sensors from Ford with a different part number. Has anyone successfully swapped their sensors with an alternative part and would be willing to share the part number you used?

Would appreciate any insight.

 

From what I've been able to dig out, I believe the Ford part numbers are:
XC2F-9F472-B1A for the upstream sensors (green sensors pre-cats), with alternative NGK 22500
XR3F-9G444-B1A for the downstream sensors (blue sensors post-cats), with alternative NGK 22106
Someone please correct me if I am wrong.

 

Just a general comment about replacing O2 sensors in pairs.

The critical sensors are the ones closest to the exhaust, pre-cats. One on either side. These are sometimes marked Bank1 sensor 1; Bank 2 sensor1; or Bank1 upstream sensor; bank 2 upstream sensor.

These two sensors play a major role in fuel trims (LTFTs and STFTs). The downstream sensors or ones marked sensor 2 or even sensor 3 are always check sensors and they validate the condition of the CATS.

If I have an upstream sensor fail. especially with some mileage accumulated (40,000 miles or more) I will replace in pairs BC, if one is becoming "tired" and no longer switching fast enough, or has failed completely, the other upstream sensor is possibly not long for this world either. If it was a fluke (and it happens) that an upstream sensor fails with low mileage and probably a defective sensor, then I might only replace one.

The downstream sensors I replace one at a time regardless of the mileage.