Both lambda sensors varied in readings with engine running from 700 something down to 70 something but values variations were constant , graph was constant .
Bank 1 Sensor 1 (pre cat) and Bank 1 Sensor 2 (post cat) Lambda sensors will/should read differently.
It's hard to explain what Sensor 2 should read as the heat of the cat effects it's performance, but it should not copy Sensor 1, but smooth out what sensor 1 is doing!
I had a little trouble like this in our old Active, it turned out it was the heater element in Sensor 1 failing.
There's two parts to a Lambda sensor, the heater element.
This allows the sensor to reach a working temp quicker than relying on exhaust gas to warm it up.
And the signal generator.
Heat passing the tip generates a voltage, the hotter (lean) the higher (0.9v).
With the heater working, but no engine running it should report 0.1v.
If you get 0.0v, it's likely faulty.
With your scan tool plugged in, make a cold start (in the morning) and monitor the fuel status.
From cold it should start up and run "Open Loop" for a few minutes as it warms up.
It will run like this for a while until the PCM detects some engine warm up then trip into "Closed Loop".
The PCM uses the coolant sensor AND it also needs to detect a quick enough voltage switch from the Lambda (sensor 1) before it enters "Closed Loop", for this timely voltage switch, it needs to preheat the sensor.
Without either the Fuel system will trip into "Open Loop - System fault", it'll use pre set values, it'll run like a dog and use up a lot more fuel.
So now if the coolant sensor is rising, yet it's tripping Open Loop - System Fault", it's likely the pre cat sensor isn't self heating quick enough.
(you could swap pre and post sensors around and test again)
If it enters "Closed Loop", this now means Sensor 1 is trimming fuel.
A perfect fuel trim will alternate or "switch" between 0.9v and 0.1v (perfect overall trim is 0.45v), you'll probably need to raise the rpms to a steady 1000 or so to get it to even out so the switch happens every second (or just under).
Higher or lower readings and the PCM is detecting a lean or rich mix and is trying to trim it out. This is often due to air leaks, exhaust leaks, faulty injectors.
If all that checks out, log Sensor 2 at the same rpm as above.
The cat should now operate to alter the signal by uses heat and stored O2 to smooth out the switching.
The log trace should not switch like Sensor 1, if it does the cat is not working properly, either because it's cold or faulty.