98 ranger 4.0l o2 sensor bank 1 sensor 2 help
 

Good morning. i ran my scanner on my truck to day and my 2 bank 1 sensors seem to be bouncing between .150 and .700 but my bank 1 sensor 2 seems to be stuck at 680-720 and not bouncing, is this normal?
i did pull a code po135 heater circuit malfunction BANK 1 SENSOR 1
Also im not sure where my fuel trims should be
my
ST1 10.0
LT1 25.0
ST2 12.0
LT2 25.0
closd loop.
when i first got the truck i pulled codes for lean bank 1 and 2 also a cylinder #4 misfire and the bank 1 sensor 1 heater circuit. i reset the codes and the heater circuit bank 1 sensor 1 poped the mil light in 5 min. so im starting with the o2 sensors. iv not found any vacuume leaks at this point.
thanks

Welcome to FTE.

Are the fuel trim numbers + Positive. or - Negative?????
+ numbers indicate the computer is having to Add fuel to compensate for a lean air/fuel ratio. A - number indicates it has to Subtract fuel because on an over fueling problem, causing an overly rich air/fuel ratio.

Its normal for the upstream/before cat converter O2 sensors to switch fast within the range you posted & for the down stream/after cat converter O2 sensors output to remain steady, if the converter is doing its job.

The P0135 code suggests that their is a heater problem with the upstream bank-1 O2 sensor. This will cause the O2 sensor to be slow to heating up & coming online.

I had a similar code a couple years ago. Ended up being a leaking egr valve. There's a diaphragm in it that tends to go bad after a few years. Gives a lean reading and essentially allows unfiltered air into the engine. Might do a smoke test before spending $ on O2 sensors and such.

After re-reading your post I see I didn't answer your after cat (bank-1 sensor-2) question. Yes its normal for the after cat O2 sensors output to be fairly steady, as its normal for it to have a fairly flat curve & not switch like the upstream sensor), if the cat converter is healthy & doing its thing.

^+1 on a smoke check to find vacuum leaks. If you come to suspect a vacuum leak, you can do a home made check by blowing smoke (aroma of your choice) lol, into a vacuum line to check it, or the intake manafold, or any other vacuum operated system thats suspect.

More thoughts for consideration, keep us posted on your trouble shoot.