DodgeTalk Forum banner
Status
Not open for further replies.

p0138

30K views 16 replies 6 participants last post by  hemi_jeff 
#1 ·
This morning the CEL came on with code p0138 (o2 sensor bank 1 sensor 2 high voltage).

The exhaust smells a bit rich but I have detected no loss of power.


Does this mean the o2 sensor is bad?

Thanks.
 
#2 ·
I get this lil bugger allllllll the time! Still have not ponied up and replaced the o2 sensor. I havnt noticed a loss in mpg or anything, but I also thought my truck was running a touch rich. I dunno. Whenever it comes on I either deal with it or get out the superchips and delete the code and it stays away for a while. If you end up replacing your o2 sensor let me know if that fixes it. I thought I Read about guys replacing thiers and in a year it came back on. I dunnno, keep me posted!
 
#3 ·
This might not be right, but if you are in fact running rich, then replacing the O2 would not solve the underlying problem and the new O2 would just go bad after awhile also. I don't THINK they can withstand unburnt fuel burning on them, even though they can take regular exhaust gas. The fuel at it's flashpoint causes more heat than regular exhaust gas. That's all just a guess, but makes sense in my head.

It could run rich for a variety of reasons, but the primary meaning is not enough air mixing with the fuel. The first place I'd look is at the air filter, and then leak test the intake assembly and clean the throttle body. Hemis seem to be picky about having the correct A/F ratio. After all, sensors are there to tell the pcm if something is wrong. They do go bad themselves, but they're entire purpose is to tell you there's a problem. Finding out if people that get this code on a regular basis have some mods in common might also help.

*EDIT* I did just notice that both of you have the same aftermarket air filter, and coincidentally the same muffler. I don't know how the muffler might cause a problem upstream, but you can't rule anything out.
 
#4 ·
Yeah I to also noticed we both have magnaflows and a k&n air filters....now Im trying to think when my code came on. It was probably about 4-5k miles after my exhaust got done. Im pretty sure I had the k&n well before that also. I actually took off my Air Raid MIT and put the stock air tube back on and nothing had changed. Its weird, my code sorta comes and goes as it pleases.....I noticed most of the time when it comes on is in the morning when I start the truck and it seems it would be when it was "damp" out or raining. Sometimes I would let it go and it would go off and others I would take it off with the tuner. Sometimes it would stay off for a day or so and other time it would stay off for a couple weeks, so I dunno.
 
#5 ·
I had this problem about a year ago, it was a bit confusing because I have a 03 4.7 and it only has 2 sensors, 1 before the cat and 1 after the cat, so I replaced the sensor after the cat and the problem went away( not that it made any difference to the way it ran) and it got rid of the light.

Robin
 
#7 ·
Bank 1 Sensor 2 is the drivers side after cat 02. Rich mixture causes an oxygen demand. This demand causes a voltage to build up, due to transportation of oxygen ions through the sensor layer. Lean mixture causes low voltage, since there is an oxygen excess. Like Ceri said, start checking anything and everything that has something to do with your air intake. From the filter all the way to the intake manifold. Are you sure you don't have a "sweet" smell. A sweet smell is indicative of a failing cat, which could also give you a high voltage read out on your o2. If the cat isn't properly filtering the gas coming from your exhaust.
 
#8 ·
How long after you start the vehicle does it take for the light to come on?
 
#9 ·
Not 100% sure, probably around 3 minutes, all city driving since this problem started so not very far either, comes on even before I've driven 1 mile.
 
#10 ·
Have you noticed a drop in fuel mileage?
 
#12 ·
I'd have to say yes to that question, I've usually gotten around 10 city and i am down to about 5-6. I unplugged and replugged in the sensor earlier (light hasn't come back on since) and fuel economy seems to be slightly increasing. I'm thinking maybe the sensor is on it's way out but not fully out yet.
 
#11 ·
If you haven't found an answer for this by morning, I will go through my computer at work and narrow down the symptoms for this.
 
#13 ·
I work at autozone and when its cold out, i see numerous people coming in with cel for this o2 sensor and a good portion of the time its a fluke cause if the vehicle dont worm up perfectly it causes the light to come on for this. Temperary false reading. On these the light was reset and no problems afterwords.Dont know if its the o2 sensor on its way out or another problem or if its caused by the computer not adjusting to the cold air quick enough, but its common on lots of diffferent vehicles.
 
#14 ·
I have noticed a drop at all. Now with the "winter fuel" mix I have but nothing from the light. But I may end up just replacing it and see if it comes on agian or not.
 
#15 ·
A code P0138 may mean that one or more of the following has happened:
-Faulty O2 sensor
-Short to battery voltage in O2 sensor signal circuit
-High fuel pressure (not as likely)
 
#16 ·
Thats the best Mitchell's came up with. Without being able to run a diagnostic scanner on it, I can't be more accurate.
 
Status
Not open for further replies.
You have insufficient privileges to reply here.
Top