When my check engine light came on I took my 02 sc430 to my favorite repair shop.My mechanic downloaded the computer and told me that the passenger side # 1 O2 sensor had failed.He checked his suppliers and he came up with an aftermarket direct replacement O2 sensor.He cleared the code,installed the O2 sensor and I was good to go.The car runs great,but my highway mileage has dropped from 28.5 to 22.5 mpg !!!Was othe old sensor running the car lean or is the aftermarket sensor not doing its job? What do you think?

 

I have a 2002, and the same thing happened to me... although mine went from HWY 24.5 to 21mpg in Power mode. My average City driving also went down about 3.5mpg.

I'm not sure which O2 sensor was changed, but I had dealer-service look at it and they said all was functioning normally.

My current belief is that our original setup gave exaggerated numbers and that the new setup (with new O2 sensor) is more accurate. I base this on a recent thread of SC430 owners' MPG.

https://www.clublexus.com/forums/sho...d.php?t=254454

Let us know if you find out otherwise...

 

Was the battery reset during this time? If so then the MPG computer will reset based on the mileage it has accumulated. For example, if you accumulated 1000 miles at an average of 24mpg and then drove all day at 21mpg the effect on the overall average will be minimal.
Now if you reset the computer the mileage will have much more on an impact as the average sample is much lower-say 10 miles.

 

I did reset the mpg computer.Yesterday I disconnected the negative terminal for three hours,cleaned the engine ground and the body ground reset the mpg computer and took the car for a 100 mile trip.Mileage went up to 24.3mpg!

 

Hey G02 - keep an eye on your mileage over the next week or so.

Whenever I reset the ECU (battery,) I get better mileage the first couple times I take out the car, but then it goes back down to the lower levels.

 

I wiil keep an eye on the mileage over the next week.