I have a 1999 V6 automatic mustang fastback 149,000 miles (not GT), and I recently got a PO156 code saying something was wrong with an O2 sensor (bank 2 sensor 2). After closer inspection, my X pipe is missing a catalytic converter, and a few of the O2 sensors are fused to the pipe (looks like heavy modification, it was an auction car). I'm going to replace the X pipe, but my question is whether the upstream and downstream sensors are the same for each bank. Can I just get two upstream and two downstream or are they more specific parts? I'm looking at the denso 234-4610 (downstream) and denso 234-4640 (upstream) as according to Amazon they fit my car.
I would find the OEM part number and buy them. I do not recommend buy aftermarket oxygen sensors.
They are the same, but here is the problem: if you don't have catalytic converters on the car, you are fixing one issue to cause another. If you replace the sensor, it is going to pop a code for the converter as it isn't present to burn the fumes it normally would.
Instead, get these:
https://www.lethalperformance.com/upr-96-04-mustang-mil-malfunction-indicator-lamp-eliminators.html
Easy install and magically no more check engine light for 02 sensor codes.
