Vehicle came in for rough running and the fuel short fuel trims were sitting on +25 long term was -30.5.
i have measured the voltages at the ecu for the oxy sensor (titania type) and the voltage was 4.97 (appears to be lean output), i pulled the sensors out and tried all sorts to make the voltage decrease to mimik a rich mixture but they didnt move at all,
i have fitted 2 replacement sensors (NTK)
now both are reading 0.05 volts (rich) i can remove the vacuum hose to let more air in, the sensors start moving and cycling as per normal, the fuel pressure is only 30psi and goes to 38 with pressure regulator hose disconnected.

questions are my sensor supplier says that 0volts is lean and 5v is rich? this contradicts what i have found as removing the new sensor from exhaust and still plugged in i have 3.8v and rising which indicates lean,
who is correct here?

how can i reset fuel trims?
what can you point to to lean it off?
coolant sensor appears correct with operating temp, fuel temp sits around 38deg.


any pointers for me