This snapshot shows the transition from open loop to closed loop control. About a minute after engine cold start on the 96, I revved the throttle slightly and the ECU momentarily jumped the long term fuel trim (blue plot) off scale high to enrichen the mixture. Less than a second later, both OX sensors showed the momentary rich condition then returned to lean. At this moment the fuel system went closed loop and the short term fuel trim (red plot) began to be changed by the ECU. Short term fuel trim was raised until OX1 indicated rich again, then short term fuel trim was lowered until OX1 showed lean. And so on for the closed loop control of mixture using the OX1 sensor. The 95 Previa will not go into closed loop and the fuel trims and OX sensors all remain at zero values.
Monday, January 30th, 2012 AT 11:24 AM