I am getting codes P0136 and P0141, both for bank 1, sensor 2. The previous owner had a local garage install a new catty, and all new pipe from therein back. It was a PA truck, so It didn't need properly working emissions controls to pass inspection. I just replaced the front O2 sensor, and am still getting codes, but for sensor 2. Does this mean that there should be a 2nd o2 sensor somewhere behind the catty?

 

yes there is 2 o2 sensors one in front of cat one in back of cat .my 96 2.3 96 ranger has two .has your fuel mileage gone down hill real fast.

 

sensor 2 would be the one after the cat, but that does not usually depreciate the fuel mileage, it is there to monitor the proficiency of the cat.

 

i am only getting about 310 miles to a full tank and should be getting around 400 miles

 

the check engine light came on in my 96 ranger splash 2.3 .
i took the truck to auto zone.they checked the computer .it said that the front o2 was bad.bought new one.mileage came back to normal .aboit 22.my truck has over 189000.still runs good.unhook the positive cable from your battery for about 2 minutes it should clear the bad code.

 

There are two sensors total... one oxygen sensor between the cat and the engine (Bank 1, Sensor 1) and one behind the converter (Bank 1 Sensor 2)... I'm wondering if they installed a "generic" cat that didn't have a threaded hole for the rear sensor... so instead just left it unplugged...?

 

As mentioned already, the second O2 sensor doesn't do anything for fuel mixture. Its there purely to monitor the efficiency of the catalytic converter. Since I don't like replacing parts that don't directly effect the functionality or safety of the vehicle, do a search for "CEL eliminator". For less than $5 in parts, you can rig up something that fools the computer into thinking that the rear O2 sensor is present and functioning properly. Better than spending $40+ to replace a O2 sensor that doesn't do squat to insure the engine runs well. It also comes in handy should you remove the catalytic converter entirely.

The converters on Rangers don't have a O2 sensor bung in them, BTW. The 2nd sensor threads into the pipe a few inches after the converter.

 

It burns gas quick and engine light turned on. The truck turnes on but then turn off followed by a rough bug out shaking noise.