About 6 years ago I bought Discovery 2 as a project. Its in nice shape but the original owner literal fried the main bearings requiring a engine replacement so I replaced it with a used good running 4.0 of the same (SAI) The used engine runs nice but I've never been able to get rid of the 02 sensor code (Bank 2 Sensor 1 "No Activity") in addition to FUELSYS2 OL-FAULT since. Throughout the last few years I've done the following by

Reprogramming the ECM by a professional
Installed 4 new Bosch 02 sensors up and down stream
Replace (used) engine wiring harness and inspected it for breaks and cracks before installed.
New fuel pump (SAI)

Unfortunately I still have the same sensor/ fuel codes/problem. (coincidence?) All the other sensors seemed to be working fine (no codes there) I've been unable to smog the car especially in California and I've only been able to get a few temp papers to drive it. Is there a possibility that I may have missed some grounds when installing the replacement engine? The battery grounds all appear to be hooked up, the firewall strap on the drivers side is attached. Suggestions?

 

Good news is you can use data to analyze your problem. On cold start your 02 sensor voltage should be close to 1 volt, so get an android torque app or some other app where you can chart the voltage, not instantaneous reading i.e. digital. You need an analog chart. If it starts near 1 volt and then goes to zero it is not the ECU, wiring, or sensor. If it starts close to zero and never changes then it probably is one of those. So I like to start with replacing easy to change component with known good components. So your code is B2S1, so swap those left and right and see if it follows. If it does not, then the next step is to ohm out the wiring and make sure nothing is shorted to ground and you have continuity from ecu to sensor. If you still don't find your problem, try swapping out the ECU/BCU combo. You can buy a used one on ebay and then resale it after the test if you don't want a spare. Report back here each step and we will help you.

 

Thank you for your response. It never occurred to me that the BCM could be the problem so I will check it for loose connections and keep you updated.