So I was driving my 2005 LS430, and got the dreaded "bong" chime. Check engine, TRAC off, and VSC lights all illuminated in a terrifying display of yellow and red. This was also during a night that a huge coldfront moved in, so I'm not sure if that has an effect. I had driven it a couple times after that, and on a third drive I noticed that the warning lights did not come on for about 10 minutes before they re-appeared. I took it to Autozone after work and they put their scanner on it. It came back with a code P0031. From my research, it looks like that is the Bank 1 Sensor 1 (pre-cat), which apparently can only be replaced by getting *under* the car and removing one of the underbody covers. I have also heard some people say that they replace their Bank 1 Sensor 1, and then the car tells them the Bank 2 Sensor 1 needs replacing shortly after. Meanwhile other people replace the one sensor and are good to go.

So here are my questions:

1. Is it normal to have a scenario where the warnings appear, and then after a few drives, they disappear and come back?
2. If I replace my Bank 1 Sensor 1, do you think these warnings will go away or is it likely that I will get another code to replace the Bank 2 Sensor 1?
3. Any tips for doing this job?

Thank you!

 

the pre-cat sensors are pretty easy to replace, i just did both of mine about 2 months ago and the whole job took maybe an hour which includes jacking the car up and putting it back down. my check VSC light is now gone. you will need a special o2 sensor socket wrech, which you can get on ebay.

 

How is your car performing? Any other issues other than the warning lights? If all else is well with no issues, personally, I'd clear the trouble codes and see if and when they reappeared and then go from there. Good luck and let us know how you make out.

 

A couple of years ago my 2004 LS430 had the P0031 code when I scanned it at home. Before the CEL happened the unmistakable faint exhaust smell would intrude into the cabin when I was stopped at a red light. If the car is in motion no smell.
So I searched this awesome forum and came across corroding exhaust pipes. With this info I took it to an exhaust shop and indeed there were already small holes just aft of the oxygen sensors. It could still be bad sensor/s, but I had to fix the exhaust first which the shop fabricated very nicely in stainless steel. I reset the computer and the car has been CEL free since.
The CEL code must've been a result of the leak.
Look into this perhaps that's what you have. Hope this helps.

 

Wow I didn't even think about this one. I'm not noticing any exhaust smells when the car is stopped, so I'm thinking it is truly the sensor.