curiousB

What year is your LS? It could be the software in the ECU is different in my car and has an added test to validate the catalytic converter. I don't doubt what you are saying. Case in point I've been two weeks without a P0430 which was my original complaint.

The P0156 though is a new one and I haven't seen it before. My thinking is that spacing the O2 sensor has the effect of reducing the gas fluctuation across the O2 sensor. Which is the way to stop the P0430 codes. But in my case it seem to trigger the P0156.

Anyway I've reset the code and will see if this P0156 is recurring or just a random issue.

As for replacing the secondary O2 sensor because it is lazy doesn't make sense to me. For the secondary O2 sensor this is what you want. Lazy O2 sensors are a problem for the primary O2 since they are used to trim the EFI fuel/air mix to so called stoichiometric point. It would be a real problem if the primary sensor is lazy. I was popping P0430's because my secondary sensor was too active (i.e. unlazy) The ECU interprets this as the catalytic converter not doing anything (acting like a pipe and gasses pass through with no change to them).

Lynzoid

2001...
not just lazy, usually sensor that is about to go will fall asleep at 0.075v for prolonged periods, then wake up and float at normal voltage. you can check that with obd2 tool.

curiousB

Update. In the end it was a leaky pipe after the secondary O2 sensor under the heat shield. O2 sensors and catalytic converters were never the issue. See link below for more detail.


http://us.lexusownersclub.com/forums...howtopic=70886

Lynzoid

Ah ! It turned out to be the hole in the 'pants' - that's how we call Y-tubes =)
Glad all is ok !