Short version - where is the connector for the rear O2 sensor?
Long version - I went to get my car inspected, today, and it failed with the P420 code. The CEL wasn't illuminated, or I wouldn't have bothered taking it to the inspection station. (The CEL does illuminate if the ginition is on but the car isn't running, so I know the bulb is there.) I bought an OBD-II scanner from Harbor Freight to read and clear codes, did both, and after another 25 miles, the code hasn't returned.
I back-probed the front O2 sensor connector, and the voltages on my Harbor Freight voltmeter varied back and forth between a minimum near .19 and a maximum near .91; I gather this means the front O2 is good. I was going to backprobe the connector on the rear O2 sensor to see if it was good, but the wires disappear into the body. Where is the connector so I can check voltages to make sure my rear sensor is also okay?
In case it matters, I bought the car a few months ago, (with 170K+ miles) and I think it sat a while prior to my purchase. I have put a few thousand miles on it, already. I think possible cat problems from sitting have since burnt off, hence the MIL ON flag but no CEL, but I am not sure, since I am new to OBDII Miatas, and have only done basic maintenance for a friend on a 91. If I do need a cat, any recommendations for exhaust shops? I would prefer to get a cheap, high flow cat if it won't throw codes, and then I'll have an excuse to re-do my exhaust every few years (when it goes bad) rather than pay through the nose all at once to get the stock cat.
Thanks for the help.
