my girl has an 03 mitusbishi outlander, her sel light has been going off and on for a good month or 2. got the code read, p0138 o2 sensor b1s2, is all bank 1s are pre-cat? and how can i tell which is sensor 2? cant find a damn diagram online. i dont want her to pay to change them because it looks pretty simple to install, and i think its got a plug so no splicing is necessary.

also, is there anyway to clean the sensor out? if so with what

thank you in advance

 

Not all Bank 1 are pre-cat. On Blazer's for example B1S3 is post cat. I'm fairly certain that B1S2 is post cat in your case. If you need to change it out, best if you have an O2 socket. You'll probably need to apply some PB Blast. Don't know if it is accessible enough to be safe, but sometimes I need to use heat from a torch. Your call on the safe use in this case however. I believe all HO2S have plugs.

 

yea the guy at advanced who ran the scanner didnt seem like he was very knowledgeable, when he told me it was an o2 sensor i asked what bank and sensor, looked lost. finally another guy came in and told me b1s2. i asked if it was post cat, and he said probably not. so who knows haha.. im trying to figure out where i can find out how many there are in her outlander. i found two when i was under there, one pre and post. but for all i know theres more. also is it possible theres only one bank?

 

If it is an I-4 engine, then there will only be one cylinder bank. If it is a V-6, then it will have two banks. B1S2 in your Mitsu is the post-cat sensor and unless it has a full dual exhaust until after the catalytic converters, it should only have one post-cat sensor.

 

that is very helpful thank you! it was a denso i believe so im not sure if thats what came with it. now my next question, the wiring looked fine, i dont think its a short causing it. or is there something else i should check, or just go ahead and replace it and that should fix it?

and being a post cat sensor, does that affect anything else (meaning is it a job i should take on asap, or can wait it a little)

 

Post-cat sensors are catalyst monitors only and have no impact on the operation of the engine.

I usually do not recommend blind replacement without some form of testing, but testing requires the proper tools. If the pre- and post-cat sensors are the same part number, you can test the sensor by swapping it with an upstream sensor and seeing if the code changes to indicate the new position. If it does, then it is safe to say that the sensor is at fault. If it does not, then there is a problem with the wiring.

 

so it doesnt run the fuel rich or anything? see the guy told me id probably have to splice it, but from what i saw online, there were two different ones so im assuming they arent the same.

would I be able to remove the o2 sensor and see if its really dirty or would it be something not seen by the eye? im just worried if i replace it, theres a bigger problem causing it to be dirty and dont wanna waste money on a new one if its just gonna clog up again

 

I agree with swartlkk that people many times waste money replacing a HO2S when the thing is doing what it was designed to do...tell you that there's a problem with something else. This page states if it's not a short, it's probably a faulty sensor for this code OBD-II Trouble Code: P0138 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2) . Though high fuel pressure is mentioned, it states "not likely". I don't know anything about cleaning them. Haven't heard of anyone trying that personally. Maybe you can get girlfriend to cough up $25 (or you could spend the bucks yourself for her as an early Bday gift LOL) ) for the Alldatadiy.com for her car and then you could follow whatever the manufacturer's troubleshooting steps are for this code on her truck.

 

As I stated, the S2 sensor in your truck is a catalyst monitor only. They have no influence over the fuel supply to the engine.

If you buy the one-size-fits-all junk, you would have to splice in the sensor, but I will never recommend that route. You are much better served to get a high quality, direct fit sensor. Denso sensors are good sensors with above average activity out of the box. The out of the box activity is a direct relationship to how long the sensor will live.

If the sensors are the same in all locations, I would recommend putting the new sensor in the S1 location (pre-cat or upstream) and moving the old S1 sensor to the S2 location. Catalyst monitoring sensors do not require all that much activity to do their job properly while upstream sensors do.

What does the vehicle have for a motor/drivetrain?

*EDIT* - They all had the 2.4L I4 engine in 2003, but for some reason the drivetrain configuration makes a difference..

Looking at RockAuto.com, the pictures for the upstream & downstream sensors show very different connectors so swapping them is out.

 

Unfortunately for her. Her bday passed hahaha...nah ill definitely look into that site, didnt know there was a site for that info so I learned something else new lol. Thank ypu guys so much for the info!! Very very helpful