O2 sensors - replacement schedule

[LennyLexus]

All,

I don't know where the myths of o2 sensor replacement intervals come from for IS250's or Lexi in general. There is no mention off routine replacement in the service schedule or user manual. Lexus Birmingham also have confirmed only to replace if faulty.

My P0171 and P0174 errors nearly had me replace all four of my sensors 100k/12 years old, this would have been £800 for parts from Lexus, £400ish Denso parts from RockAuto and German suppliers. Most mechanics don't want the hassle challenge of fixing these lean errors, one of my mechanic mates called it the "blue screen of death" for Lexus/Toyotas.

I found a great mechanic that professionally tested all my O2 readings FOC and confirmed it was not causing me any issues, the problem lay else where. He then offered to find the problem for a maximum cost of £60!!! Lexus was starting at £200. And indeed he did find the problem (a loose breather pipe).

Lesson is... get your sensors tested properly before replacing them willy nilly. I used Tiburon Auto based in Birmingham, they are high regarded in the Korean car club community and also used by one Birminghams top supercar hire centres.

Len

[The-Acre]

That's good info.  I've got one I apparently need to replace but just because it throws up a code showing which one, I'm still not convinced as the "check VSC" comes and goes.

[ColinBarber]

It's a fact that the upstream sensors tend to fail, become slow, or the heaters fail between 60k and 100k miles. A fault code relating to the O2 sensors doesn't mean the sensor is faulty - as with anything you still have to diagnose the issue.

Breather pipes should just fall off, if you get an error code shortly after work has been performed on your vehicle then there is obviously a good chance that something has been disturbed or not fitted correctly.

[LennyLexus]

48 minutes ago, ColinBarber said:

A fault code relating to the O2 sensors doesn't mean the sensor is faulty - as with anything you still have to diagnose the issue.

That's the main point Brains. All my sensors were tested and shown to be within optimal working range. 

Do you think it's a case of when rather than if for for the upstream sensors to need replacement? The same for the water pump? I'm currently just under 100k. If that's the case I'll buy from Rock and keep in stock.

[ColinBarber]

Yes, the heater circuits will burn out eventually, and those error codes are accurate - if the heater circuit becomes an open circuit it is easy for the ECU to determine this.

Even when the O2 sensors themselves still seem to be working they can become slow to react which causes a slow deterioration in mpg.

Water pumps can last 150k miles but most people will replace when replacing the timing belt as the labour cost can be the biggest expense. Normally you get a bit of notice that a pump is on the way out, either it starts to leak or whine. On the IS200 it isn't too serious if the pump seizes because it isn't driven off the timing belt, you just run the risk of overheating the engine if you don't notice quickly.