P2238 CEL

I've cleared this code about 3 times over the past month. It's a definite problem.

Any recommendations on checking for causes. Any definite or successful fixes?

Heres what I read in the FSM of probable causes...

- Open in A/F sensor circuit
- A/F sensor
- A/F sensor heater
- EFI main relay

 

Most likely cause is the A/F sensor. You need to ohm out the wires on the sensor with a multi meter. 2 of the wires should have an ohm reading. All other wires on the sensor should not. If all the wires show open then the sensor is bad.

Edit: there should be 4 wires on the sensor (if I remember correctly).

 

Thanks Nelson. If I replace the AFR sensor, should I replace the o2 sensor also?

 

You may want to hold off on getting that AFR sensor before you do your O2 sensor. My book shows that P2238 code is : O2 sensor positive current control circuit low, bank 1 sensor 1. This is your front O2 sensor on your driver's side before the catalytic convertor, and I believe this is your problem.
I don't like the idea of throwing parts at a problem, and you can test the O2 to make sure it is bad, but I believe that the O2 sensor is bad and throwing your code. Testing requires back probing the sensor as the truck runs and this may not be easy to do. If the O2 sensor has never been replaced, you may want to do that before buying the AFR sensor.
This is just my opinion and I am sure there will be others, so read them all and decide your course of action. Good Luck.

 

An O2 sensor is the same thing as an A/F sensor. FYI

http://www.autoshop101.com/forms/h37.pdf

 

No. If it was needed there would be a code for that also. Let us know how it turns out.

 

What the... My parts guy at the dealer is asking $180 for the part. Says the California o2's cost more.

Anybody know where I can get it cheaper?

 

I live in Ga., But I looked on Autozone and they want 118 for the Bosch Brand sensor. I hope the one in cali.should not cost more, but you may want to check for one. You do not need to go to the dealer, as there are alternatives, so you may want to check all your local auto parts places. Good Luck

P.S. you may want to start spraying some kind of rust penetrant on the bolts that hold the O2 sensor and let them start to soak. Those bolts can be tough to take out.

 

Thanks for the info. Ill spray some pb blaster for now and swap it out over the weekend.

I found the connection... Easy to find under the shifter boots inside the truck. I was able to remove it from the clip holding it to the top of the tranny. How do I disconnect? Do I squeeze with pliers or is there a slot for a small screwdriver?

 

Good Luck, here is a link to pictoral on changing out the sensor. http://autodiyonline.com/toyota-diys/toyota-tacoma-diys/toyota-tacoma-1995-2004-3-4l-oxygen-sensor-replacment-diy/

They recommend breaking the plastic clip that holds the wire to the transmission and then unplugging the wire. I would guess that you will need to squeeze the plastic clip on the transmission side of the wires. Be careful, as those wire connectors will be old and the plastic will be fragile.

The PB buster is a fine choice for a penetrant. I hope this is a easy job for you, you sound like you have turned a few wrenchs before.

 

Will the P2238 code prevent the truck from starting/running? Mine just came on and I've cleared it 3 times but the truck runs fine.

 

No the code will not prevent the truck from running, there are very very very few codes that if set will do that. P2238 is emission related, thus its not going to effect how the trucks runs, at least not to any extant you should notice.

 

Thanks man, I'm not going to worry about then since my state doesn't have inspections. The light came on during a road trip, ended up averaging 22mpg so I knew it must not be too bad.

 

Go with a Denso sensor. They are OEM. Lot of folks have had issues with the Bosch ones.
More than likely you can get the part on Amazon and have it in your hands in a couple of days.