Hello, This week our 2010 Prius (about 75,000 miles) was forced to go through a small plowed bank of snow left in the middle of the road (nothing huge mind you), and within a minute the check engine light came on solid. The light has never illuminated for an issue before, until now. The first time I tried to read the codes, I used my scan gauge II and just got P0000. Not realizing it might not be reading the codes properly, I just deleted them. But the light came back on again the next day. I tried a different scanner and got P0138, P2195, and P0138 again (in about 40 miles of driving). I've looked under the car 2x looking for any obvious damage and I don't see anything. The first time I just put the front up on ramps. The second time I jacked up one entire side and looked at the whole underside all the way to the back. I've checked the codes by googling and searching this forum already and only found limited help, and seemingly for different situations. There's a very small ding in the bottom of the exhaust canister that is immediately downstream of the downstream 02 sensor, or in other words, the first canister in the exhaust system where the exhaust finishes angling down from the engine and starts running horizontal under the car. The ding is small though. The wires on the 02 sensor just before it look fine. What I presume is either the upstream 02 sensor (or the air/fuel ratio sensor) further up near the manifold looks fine too and seems to be buried to far up to have received any damage anyway. No wires ripped or frayed, and again, no obvious damage. Any ideas where to go from here?
I would inspect the O2 sensor again -- it's pointing to the downstream sensor. It may have been hit in a way to damage it? Inspect that the plug was not pulled. Although it is indicating "high" so I bet damaged. I'm not a believer in throwing parts at cars -- except when the code points to a specific part. Check the price on Amazon for an exact replacement -- the downstream should be a simple sensor. If you take it to a shop and the codes point to the sensor -- they will replace it. It will end up a $350.00 service -- The last simple sensor I replaced was $90.00. Spray the sensor with some penetrating oil and use the correct tools if the space is tight. Don't get anything on the new sensor. I never use universal sensors -- it's not worth the price difference. Getting the exact sensor makes the job easy.
Good thing I came in to check my post today! I had email notifications turned on but didn't receive any so I figured my post didn't have any replies (and I apologize for the delay). I will check the sensors again, particularly the lower one, but it did look perfect. It sits just above a splash shield that itself didn't have any damage. The harness was still plugged in, though maybe what I'll try to do is unplug it and plug it back in. I have to do an oil change anyway so I will be taking the pan out to get to the filter/drain plug on the engine. But I've cleared the code a few times and it just keeps coming back. So whatever it is, I will have to deal with it. I'm used to 02 sensors lasting much longer on Toyotas, though we did have a 2nd gen. Rav4 and those do tend to go through sensors for some reason. While I don't want to throw parts at it either, I'm sure I could buy that rear sensor and just replace it for less than the cost for the dealer to read the code for me and just tell me what I already know. What's throwing me off a bit are a couple older posts: Rough starts: rough start, throws P0138, P2195 codes | PriusChat This person had more codes and a 2005 G2 but hit a snowbank: CEL code P0138 | PriusChat It's winter time, though our fuel economy has been "normal" for winter, if anything, it's actually a bit better than normal because we've had a warm winter. We haven't had any rough starts with the car, and it lives in a heated garage. I have a couple code readers but they are cheap and 6+ years old. Is there anything newer out there that may help me tap into the sensors and see what they are measuring? Are there only two sensors on the exhaust, and both on the vertical/diagonal section of exhaust? I followed the exhaust all the way back from manifold to muffler and thought I only saw two sensors, and both were up front before the pipe went horizontal. Maybe there's a sensor further back that I'm not even seeing?
I wanted to follow up, as it appears I've fixed the issue. I was able to get 2 new sensors for a good price on eBay, so I opted just to get both. I started by replacing the rear one (easy to get to) and the code came back within 2 drives (20 miles of driving). I replaced the upstream sensor on the exhaust manifold (PAIN to reach) and that took care of it. We have about 120 miles on the car between 6 different driving cycles and no more light. It would have come on by now, so I know it was the upstream sensor that was the problem. The original sensor looked perfect and had no damage what-so-ever, so I don't see any possible way the snow bank had anything to do with this. The sensor is too high up and protected.
I'm not real sure what to think. It would be one heck of an odd coincidence to have the failure right after a snowbank and not have them be related. But yet, neither sensor showed (physical) - damage.
