After swapping the pre-cat O2 sensors side-to-side, for some reason the MIL stayed off for 2 days last W/E. I didn't drive quite as much, but it would normally have tripped.

I figured that it was definitely the Bank 2 O2 sensor at that point, so I ordered an OEM from my buddy in the morning. On my way to pick up the sensor that afternoon, the MIL tripped again, twice in fact, indicating that the lean condition had moved to the other side, following the sensor swap. Pretty well confirmed the weak or dying O2 sensor!

After replacing the sensor, my gas mileage has returned to normal, and no more MILs over the past 2 days!

Thanks to all for the suggestions and help!

 

Good that you got it fixed. Your gas mileage went down because the 02 was misreading the lean condition and causing the ecu to dump more fuel on that side. Explains why that sensor was dark.

 

Glad to hear you solved your problem, Gord.

I thought about changing my O2 sensors as a matter of routine. So, are the aftermarket Bosch not good?

I'm not crazy about paying for OEM parts if I can get better aftermarket for less .

 

Can you tell me where the locations of the O2 sensors are that you swapped? I think I have the same problem. I'm getting the P0174 code. I already cleaned the MAF and my gas mileage is suffering. It sounds like its the O2 sensor but would like to be sure. Thanks.

 

How many miles on yours?

You have to get under your car. There are 4 O2 sensors. The 2 forward of the cats are the ones that I swapped.

 

Not sure how well the Bosch would work. I've heard some ppl have problems with Bosch sensors on Japanese cars, but have no experience with same. I used the OEM one.

I may just swap out the other sensor as well next spring since it's the same age as the faulty one. Got an O2 sensor wrench which should make things a little easier. There's still not much room to even line the new sensor up to thread in by hand however.

 

Its an 03 with 39k miles on it. The only mod I have is the JWT intake with Z tube. I cleaned the MAF so hopefully its the O2. I hate getting under the car so I may just take it to the dealer or mechanic.