Hi Everybody,

I did the search but couldn't find anything related to this code P0031.

My wife RX is due for 60k service. Last week, I replaced the engine air filter and the cabin air filter (Thanks to Clublexus). After driving for a week, the Check Engine, VSC, and Trac Off warning light is come on. I went to Autozone and ran the code. It's P0031 (AF Sensor heater control circuit low, AF sensor heater relay fault, failed AF ratio sensor). I got the definition from the print out. Does anybody know what cause this or what need to be changed? I tried to push the Trac control button under the driver knee but didn't change anything. Should I connect the battery to clear the light?

I'm about to flush the coolant, drain and fill the transmission, brake fluid, and power steering fluid next week.

My wife RX is still under CPO warranty. Should I take it in even though I'm not doing the 60k service with them?

Any help is greatly appreciate.

 

Does not matter where you have your service done. Vehicle is still covered under the CPO warranty. Take it by the shop or give them a call on Monday. They should even give you a loaner car while the warranty work is being performed.

Would hold off on your to-do list until this is complete. Just in case anything they need to do takes one of those items off the list for you.

 

The broad definition of the code you mention is Mass Air Flow circuit malfunction. Since you mention that you replaced the engine air filter, might it be worthwhile to make a quick check to see that your MAF sensor is properly connected? If found unplugged the dealer might consider the visit a non-warranty expense. Some folks could be inclined to disconnect MAF to gain additional movement to get the filter element out / in.

 

I checked all connection around the air filter box and did not see any loose connection. I will call them right after Christmas.

Thanks everybody. Merry Christmas and Happy New Year!!!!