P0134 98 rodeo w/ engine swap

P0134 1998 rodeo V-6 w/ correct engine but engine has been recently changed...got code P-0134...replaced oxygen sensor....same code.

scanned: P0134 o2 sensor circuit no activity bank 1, sensor 1

any help is greatly appreciated

chris

First, if you're sure a fault still exists(it will take 3 key cycles showing no faults for the code to clear) did you replace the right sensor? Usually people replace the incorrect sensor.
Bank 1 Sensor 1 indicates the front sensor on the side of the engine that contains cylinder #1.

Bank 1 on a 3.1L it's the driver's side, but there's another 3.1L with #1 on the passenger side. On a 3.2 it's the passenger side. If you're not sure, get a book or take it to a shop.

If you replaced the right sensor and the code reset, also check for any exhaust leaks present in exhaust manifold or exhaust pipes which could affect O2 readings. Another possibility is the HO2S signal circuit or the ground circuit could have high resistance(wiring problem)