Sensors

Had the Jimny on the diag box at work today doing a live test. The o2 sensor voltage was fluctuations from 0.200v to 0.900v rather erratically. Is this normal or does it need a new sensor? Its running ok but rich the box said it was running rich then lean but flicked back to rich and seemed to stay as rich more than lean. Any ideas would be fantastic!!

This is normal. The ECU is monitoring the amount of unburnt fuel so the voltage switches back and forth. 0.2v is lean, 0.8 is rich.
In my experience the heater circuit burns out inside the sensor and sets a fault code long before the sensor its self fails. Either way you would get a fault code eventually.
I say that because the ECU has to see a pattern before it will throw up a fault code. With O2 sensors, the car has to have performed a readiness test 1st. That involves the ECU watching the sensor readings while the car starts, gets to normal operating temp, is switched off then started again.

thats normal when the engine is idling and at part throtle(closed loop).
the ecu does that to get maximum efficiency from the catalytic converter.
there is some science/chemical wizardry involved which i have forgotten:laugh: .

Haha I need to find the scientist/wizard then....I guess the sensor is t the reason the car is running rich then is it... any ideas what I should try to get it to not run rich?

If the sensor is switching between rich and lean, the ECU thinks it is running ok. What makes you think it is running rich?

It smells really rich and did 150 miles on a tank and the lambda emissions aren’t right. It’s defo not running 100% atm