koreywill

Hello all and good morning! On the way to pick up our granddaughter for the weekend, my 2003 ES300 with 356,xxx miles popped two codes: P2238 and P0031 as read by my ScanGauge 2. I read the codes, cleared them both, and the P0031 came back immediately. Cleared it and it came right back. Drove another 100 miles and P2238 never reappeared.

I've been researching this morning and what I've found is that P0031 points to the Bank 1 Sensor 1 Air Fuel Ratio Sensor (also sometimes called an Oxygen sensor) which is located before the cat on the backside of the engine near the firewall. Not the easiest to get to but it can be changed using proper tools.

I'm confused, though, by part numbers. Most of the diagrams I've looked at are inadequate and it's difficult to find the undisputable part number.

I THINK this is the number: 89467-33050. Equivalent Denso part number is 234-9047. Are those correct? If so, is Denso in this case ok to use?

I realize I've not done any checking for disconnected wires, corroded connectors, or anything else by way of testing. I will tend to that later today but I wanted to get some input on what to look for, how to test, and to get confirmation on the part numbers if I do find the A/F Ratio sensor is at fault.

Any input/guidance would be greatly appreciated.
koreywill

Arsenii

Hello,

P0031 refers to a Heater Element in a sensor, which is responsible for warming it up so that it will become efficient quicker. P2238 indicates that the sensor current output is too small; this code usually indicates a bad sensor. Check the wiring coming to the sensor, you should have 12V on two Black wires, as well as 3.3V on Blue and 3.0V on White wire. You can also check the resistance of sensor's heater element (between two Black wires), if there is none, the sensor is definitely bad and needs to be replaced.

Here you can find all the Part Numbers for your car, P/N for the sensor you are on a lookout for is 89467-33060, 89467-33050 is for a Front (B2S1) sensor, Denso equivalent would be 234-9047.

P.S. I am actually legitimately surprised your sensors lasted as long, they usually die much sooner.. 356K miles is a ton, this car is a trooper.

Hope this helps and best of luck!

koreywill

Arsenii: Thanks for the heads up on the testing of the voltage. Question: Is the voltage testing done with the key on, key on and engine running, or....?
As it was a code P0031 am I correct in that it's the sensor before the cat coverter on the back of the engine near the firewall?
Again, thanks.

Arsenii

Al voltage tests need to be done with the key in the ON position, you don't need to start the engine.
Yes, Bank 1 Sensor 1 is located on the back of an engine, right near the firewall, before the catalyst.

Hope this helps and best of luck!

koreywill

Thanks for getting back to me so quickly. Appreciate the input.

Trust but verify.

koreywill