Hello,

This is a great forum and very helpful. I own 2003 Lexus RX300 and about 2 months ago Check Engine and VSC lights went on. I have basic code reader and the only code I found was PO136. Seems like this is "Bank 1 Sensor 2". I have read a great thread about how to replace this and while it seems like a bit of a challenge, I think I can manage it..

My question is about mileage - when the dash lights came on, my mileage went from around 20mpg to around 15mpg. Everything I have been reading about the PO136 code says this issue shouldn't affect the mileage. Is this correct? My concern is I will replace this sensor and will then find out there is another issue since my mileage is sufferring. Any guidance from the Pro's? I don't have inspection in my state, so no need to replace things just to get rid of codes....

Thanks for any help with this issue

 

The sensor can be dirty too. [My bad ... sensor 2 sits in the exhaust ]

There may be other issues as far MPG is concerned, but the sensor does play a part metering the amount of gas injected into the engine. I would at the least start by fixing the error reported by the computer.

You can check for drag [see if the vehicle coasts fine].

Salim

 

Thanks for the reply - I didn't see anything about dirty sensor when I searched for issues - how do I check this?

I know many issues can cause lower mileage - my mileage dropped at pretty much same time idiot lights came on and code appeared - some people said this sensor has no effect on mileage - thanks for chiming in that it can have an effect. In all honesty, with no inspections, I probably wouldn't be fixing this unless my mileage was suffering...

Thanks!

 

O2 sensors can affect gas mileage as mentioned above.
If you have a scanner maybe you can post your fuel trims so we can see what's going on and rule out a vacuum leak if the new O2 sensor doesn't improve yout mpg.

 

I learned from Salim that the mileage calculation in your car is based on the measured O2 values before and after the engine, so an O2 sensor code that coincides with a sudden drop in mileage is probably a symptom of the sensor, not an actual drop in mileage. But your car is still responding to that sensor, so best to get it replaced on the quick.


When the check engine light comes on the computer stores readings from your sensors that can be read with your code by selecting ‘Freeze Frame’ on your reader. Those readouts include the short and long term fuel trims, aka what Margate was asking about. Toggle to freeze frame when the CEL is on, the reader should show a few pages that you may have to scroll through of your sensor readings at the time the code threw. Very helpful for diagnostics.

 

You are in limp mode. Your gas mileage will always be horrible in limp mode. You could try to clear the code and see if it goes away... or goes away for a while until you have time to replace the sensor.