03 Camry 2.4L (2AZ-FE) P0031 code

I have had this code for a while (years) and didn’t much care because the car runs fine until moving to TX and need it to pass smog check.

I replaced the 02 sensor before the cat (upstream) with Denso part 234-4209 which has to be spliced to the orig plug. The mil returned right away. I took the sensor back and got another, same result. I am hesitant to try the sensor with the plug on it Denso 234-9010 @$150.

Checked the voltage with the key "on" at the ecm side of the plug and got 9.3 volts on the heater circuit (black wires). The sensor measures good continuity @ 15.7 ohms.

No continuity from the heater circuit on the plug to ground on the batt with the key off so I don’t think there is a wire grounded and all the wiring looks good.

I was wondering if it was possible that I have an ECM/ECU problem?

Make double damn sure you have the right A/F ratio sensor. If you didn't already, give your Toyota parts counter your VIN and get a part number from them. Then get the corresponding DENSO unit. It should be a plug-in with no splicing necessary. Usually Amazon.com has them at good prices.

http://densoproducts.com/resultsApp.asp

Make double damn sure you have the right A/F ratio sensor. If you didn't already, give your Toyota parts counter your VIN and get a part number from them. Then get the corresponding DENSO unit. It should be a plug-in with no splicing necessary. Usually Amazon.com has them at good prices.

http://densoproducts.com/resultsApp.asp
Thanks for the info but thats why I posted the part numbers I used looking for someone who might have experienced a similar problem.

As I said before, I don’t want to throw $$ at it if a simple reading of the voltage from the PCU shows a different problem.

Does anyone know what the heater circuit should voltage should be?, or any other troubleshooting that might point me in the right direction?

Please pay attention to Brian's recommendation regarding the A/F ratio sensor. I MUST question why you would let a code linger for so long as this will aggrevate the original issue. You may have multiple concerns that have snowballed from the original issue :(

Please pay attention to Brian's recommendation regarding the A/F ratio sensor. I MUST question why you would let a code linger for so long as this will aggrevate the original issue. You may have multiple concerns that have snowballed from the original issue :(

Which recommendation? The link he added for spark plugs when I have a code involving an A/F senosor?

As far as letting a code "linger", the car has been running fine for YEARS and I check regularly for additional codes. Sure, it may not be running with "perfect" conditions but what car does?

I think it is pretty obvious that I did a little research since I am on this forum. I am asking here for someone who might have had a similar issue and how they resolved it. Maybe that car doesnt like that sensor? Maybe there is a bad batch of them? Maybe when you have the conditions I have described, the computer is bad? This is the type of info that might help me.

I am trying to be nice here because I do appreciate the effort to help but I MUST question why you are commenting if you have nothing to add except to critisize my earlier decisions which will do nothing to resolve my current problem. So if you haven't experienced this problem and can help, PLEASE keep you comments to yourself.