Contour Enthusiasts Group Archives Forums General Troubleshooting Upstream Heated Oxygen Sensor circuit Slow

I am going to replace my upstream o2 seonsor on bank 2. Which one is this? Is it above the precat on the frong manifold or the rear manifold. I'm getting a p0153 code.

Also, p1131 and p1151 codes, both say that I am running lean. Could this be due to fuel starvation? Or should i first replace the upstream sensor to see if it takes care of the other codes? I'm cleaning my uim and lim, along with the injectors to see if that could be the problem. Also, i hear the fuel pump turn on when i start the car. I think i'm going to have my fuel filter replaced today also.

P1131 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1.

P1151 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2.

P0153 Upstream Heated Oxygen Sensor circuit Slow Response - Bank No. 2.

Alright is it clear your O2 is bad.

Something I find odd and someone correct me but with the first two codes, bank 1 and bank 2 are both lean, does that mean an intake/vaccum leak, like it would with PO171 system to lean bank 1, PO174 system to lean bank 2.

This combined with your idle problem, I would look over all your vacuum lines get some carb cleaner spray the lines if it stumbles then there is your leak, same with the manifold gaskets if you spray on them and the engine stumbles there is your leak.

Ok guys just replaced the upstream o2 sensor in bank 2 (front of engine) and am letting the computer reset as I type. I'll post in about 10 min if there is an improvement. Thanks for all of your help guys. Hopefully this will end my problems.

Good luck! I hope so too!
If not, report back and I will try to help some more.

Ok, went for a ride, driving much better. About 10 minutes later, I took it to autozone since my cel is burnt out. It passed. No codes. Continued driving well. THEN....one time when i stoped, the idle fell well below 500 rmps, i smelled a wierd smell (mix of gas and something else), then the engine caught itself and idled very low. Drove away, pulled into my driveway, rpms didn't fall that time. So something is still up. But for about 10 minutes she drove like a dream haha.
Heres a description of the idle. It stops around 1k, then falls to 750 briefly and then falls to 500. Ran pretty firmly at 500rpms. Now i thought that maybe my needle was off my 250rpms. But then the idle almost fell to 0 that one time i stopped, so there went that idea. Whats next on the list?

You had switching codes for both O2's and only changed bank 2.
You might want to consider changing bank 1 next.
It will take 2 drive cycles of errors to throw a CEL.

I only got a code for one upstream o2 sensor though. On bank 2. No codes came up for the bank 1. Anyways, I guess I'll get the codes read again. But I just took her for another ride, and she still idles at 500 but it didn't fall below that at all, and no close stalls this trip. I didn't know it took 2 drive cycles to throw a cel. I should really replace the cel bulb.