'03 Hyandai Sonata P0138 engine code

[smokin5s]

P0138 o2 sensor high volt bank 1 sensor 2

 

I'm assuming this is a faulty O2 sensor.... so how do I know which one is bad?

[Trouble Maker]

It's bank 1 sensor 2.

 

Bank 1 or 2 tell you which set of cylinders it's on if it's a v-engine. I'm not sure if there is a set way to that, i.e. front is 1 and rear is 2, left is 1 and right is 2. But this is a 4-cylinder car so no worries there.

 

As far as I know it always goes upstream to down stream, i.e. sensor 1 is before the cat and sensor 2 is after the cat. I'm no guru so someone please confirm this.

 

 

So, while you should replace it there is no need to rush. Since AFAIK sensor 2 is only there to check the health of the cat and isn't usually used to adjust anything else in the ECU. Since it's after the cat, my understanding is it can't accurately measure AFR's. Measuring AFR's is the job of the O2 sensor that is before the cat (i.e. Bank x sensor 1). I've had them go bad on cars and didn't see any (noticeable) change in MPG (by actually calculating gallons put into the car versus miles driven) after they went bad and after they were fixed.

 

EDIT: Just saw there was a 6-cylinder option. If you have the 6 cylinder hopefully someone can chime in who knows which bank is which sent of cylinders.

[smokin5s]

it is the 6 cyl car...

[Dan1647545506]

on mitchell, code says: its a Hyundai. Id replace the car right away. Edited July 26, 2010 by Dan

[smokin5s]

if I knew which O2 to replace I would :-)

[Dan1647545506]

if I knew which O2 to replace I would :-)

 

[smokin5s]

 

I misread what you wrote.... it's my parents car and they are retired... they are on a limited budget and cannot afford to purchase a new car so that's not an option.

[99FLHRCI]

^ Engine BANK

 

^ Up = Sensor 1 = Front = Closer to the exhaust manifold = Before the Catalyst

 

^ Down = Sensor 2 = Rear = After the Catalyst

 

^ Bank 1 is closer to the dash panel = RH (right hand)

 

^ Bank 2 is closer to the Radiator = LH (left hand)

 

 

The following O2 Sensor EXAMPLES show how to interpret the terminology:

 

^ B1/S1 = Bank 1/Sensor 1 = Dash Panel Side, BEFORE the catalyst

 

^ B2/S2 = Bank 2/Sensor 2 = Radiator Side, AFTER the catalyst

 

 

Per AllDataPro

[99FLHRCI]

Bad news is they are like $137 from a dealer and it has changed from titanium to zirconium and that resulted in a change to the harness and ECM (according to AllDataPro).

[Bam]

^^^Ouch that blows....but really how important can it be if its the downstream sensor? I always thought you could remove them without much ill effect, except for the obvious CEL.

 

??

[Dan1647545506]

you can leave it. dont have to replace it asap. no worries

[99FLHRCI]

Your car will not run at the right air/fuel ratio. Do to EPA/emission laws the car will lean itself out to prevent damage to the ozone. This will hurt gas milage and maybe the engine. The Knock sensor SHOULD prevent damage to the engine.

[smokin5s]

Bad news is they are like $137 from a dealer and it has changed from titanium to zirconium and that resulted in a change to the harness and ECM (according to AllDataPro).

I need to check to see if I can get them cheaper from Autozone or somewhere else... like I said before, he is retired and on a very limited budget.