Trouble Code - P0000 P0031

It looks like Red and Green are the signal wires going to the ECU, Yellow is the Heater Circuit also going to the ECU, Black is battery voltage coming from the EFI main relay.

 

This may help.

 

Hi Swanny,

It looks like the heater within the air/fuel ratio sensor has failed open. Your ohmmeter can verify this, since dogfriend provided the connector pinout and the resistance spec of 1.8 - 3.4 ohms.

Good luck getting that part replaced under warranty.

 

I don't think Patrick meant it the way you took it.

It should be covered under the emissions warranty, so you shouldn't have any issue getting it replaced.

 

Do you have any update? I am having the same issue, first P0138 + P0031, now, after about one month P0031 only.
http://priuschat.com/forums/gen-ii-prius-care-maintenance-troubleshooting/103565-cel-code-p0138.html

 

OK! I replaced the AF sensor a month ago. The code seems to be gone.

 

folks... I see this is an old thread, but it popped up first when I went looking for code P0000. The car is a 2008 with 55k miles. I got that code along with the triangle of death, but the car seemed to be running fine. I drove a short distance, stopped and checked the codes again. This time, it was U0100. Since I didn't have my phone with me and couldn't look the code up, I cleared it and hoped for the best. The next time I started the car, I was back to P0000. Another stop, and the triangle went away and the check engine light went away.

Immediately before this started, just after I turned the car off, I unplugged my ScanGuage II and moved the connector to the side port. (It was still getting power when I did this.) That seems too stupid to have been the cause, but it was the last thing I did before I turned the car back on a few minutes later and got the triangle. Any ideas? Should I just be happy that it went away and leave it at that?

(Additional info) -- The car is due for an oil change, so the maintenance light is lit. I have the feeling this might be the cause of the P0000 code, since that's a generic code.

 

My CEL came on and am getting codes Poo31 and P2237 from my 2010 Prius III. Seems unlikely that both O2 sensors went bad at once, so I suspect the A/F ratio sensor. Is there a better explanation? Is there a good way to diagnose? Are these covered under the emissions warranty? Can anyone suggest a decent dealership service department in the Boston area? Should I have started a new thread for this? Thanks!

 

I have the codes P0031 and P2237 on my 2008 Prius. I'm not keen on spending $500-700 on this right now, so I'm trying to figure out what I can do on my own. I've understood some of what's on this thread. My question right now, though, is how long can I wait to fix this? I'm sure I'll realize I just have to bite the bullet and pay the money, but I want to know if this is something that will damage my Prius the longer I wait or if it makes it unsafe to drive. Thanks for any guidance.

 

the a/f sensor will affect the engine operation and mpg's, but won't harm anything if you can live with it.

 

For what it's worth, I just had P0000 pop up (along with 'check engine' and the dreaded RTD [red triangle of death]) on my 2007, and this was a day after I had my emissions tested.

When I started my car, the idle was really low engine sounded rough. When I got it on the street, that's when all the errors popped up. I limped home on the traction battery as the ICE (internal combustion engine) had turned off. When I tried rebooting the car, the engine would idle at low RPM for about 10-seconds, then shut down.

I checked the 12V battery, which has low voltage (11.95V) but not to the point of being the problem. After resetting the codes with my ScanGaugeII, I would occasionally get P0486 and P3190. The former is not a code I know, but the latter has a myriad of potential issues, including the MAS (mass airflow sensor.)

Since it was easy to do, I disconnected the MAS connector, then the engine would idle at a more nominal RPM, and would not switch off after 10-seconds. This is when I got P0486. So I pulled the MAS out of the car and inspected it visually, and I noticed a chunk of something — almost like a thin vein from a dried leaf — stuck to one of the probes. I used a can of MAS cleaner to ensure all foreign matter was removed from the probes, then replaced it in the engine without using the two screws to secure it, and reconnected its cable.

I reset the codes again and rebooted the car. That seems to have solved the problem because the engine idled at nominal speed and didn't shut off after 10-seconds. I screwed it back in and drove the car for a while and she seems like the same old girl I've known for 13-years.

If anything changes, I'll post the results.

MattLTH