[duffyatkinson]

Originally Posted by chinaloy

Duffy, what i meant to say was that just because the front sensors fail, it does not mean the rear sensors will follow in so much as if one front fails, it seems that the other front follows very shortly after.

I agree. But as you mentioned below, O2 sensors ARE wear items, so units installed at the same time can be expected to fail at the same time.

Originally Posted by chinaloy

As for the Bosch vs. NGk or Denso. I have not seen empirical evidence saying that Bosch is bad for Toyotas.

Didn't say bad; I said that significant anecdotal evidence indicates that the ECU in the Tundra does NOT like to work with the Bosch units. I'm not an engineer, so I can't tell you why. You decide whether you want to gamble on a German component in your Japanese vehicle.

Originally Posted by chinaloy

As a matter of fact, I just replaced my spark plugs with the oem Densos and my mileage went down and my truck cranks over more before it starts. My orig plugs had 135k miles on them and the gap was huge, but the truck ran better. go figure.

If all you did was swap plugs, then something is distinctly wrong. You either have used an inappropriate plug, or your gaps are off.

Originally Posted by chinaloy

It's electronics, the ECU doesn't care who made them, it just reacts to them.

You are correct. It IS electronics. And they rely on a certain set of expected behaviors that correlate to its operating rule set. When there is deviation (as may be expected with non-OEM electronics), then unsurprisingly there will be operating problems.

Originally Posted by chinaloy

I have come to the fact that O2 sensors are wear items and they need to be changed periodically. I used the universals because of cost. They are easy enough to change. If I need to change them out 5000 miles earlier, then so be it, they were half the price of oems.

You are correct. They have electro-ceramic components that wear during use. But the OEM Denso and/or NTK units have an expected operating life of 100,000 miles in normal service.