Oxegen Sensor Testing

[craigomatic]

Hi

Not so long ago my '94 6th gen celica failed its MOT on emissions. I tried some engine flush and razzing the car about abit but it failed again.

So I took it to Mr T to get it diagnosed. They weren't overly helpful, but they told me the sensor wasn't switching.

Back home a friend and I followed the testing method set out in the Chiltons manual, where it says that the voltage should fluctuate, but not how much. We did get a fluctuation after rewiring the sensor, but not very much.

Does anyone know how much it should be? and what the voltage should roughly read?

craig

[edwardio]

Electronic chips normally use 5volts when activating internal circuitry.

Now if it depends on the tolerences of the components used, but chips can register 3volts +, as 5volts (0volts being a logic 0 and 5volts being a logic 1. Or off & on). This is because a switching level is used due to component tolerences.

So I would guess that you should have one reading below 3 volts and another about 3 or over. Hope that helps.

[craigomatic]

hmm.

that doesn't sound like we were in the right area.

we got an initial reading of 13.3 which went up and down by .1v

so our reading doesn't sound right given what you've said

[edwardio]

The actual sensor may operate around the 12 volts mark, but the ECU will run at 5 volts. So it depends on how that voltage is reduced, to how the ECU reads it.