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Discussion Starter · #1 ·
Hi all

My engine light has been on for a while now. Before it was going on and off and now it is on all the time. I had the code checked a while ago and the shop said P0138 Bank 1, Sensor 2 error. They told me to watch it and wait until I guess the O2 sensor failed fully.

I just replaced the downstream O2 sensor (think my truck has 2, one up one down?). the light is still on even after disconnecting the battery.

Any ideas what to do next to fix the problem?
 

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bring it back to autozone or someplace that checked it, tell them you had it fixed and you want the light turned off. that should do it. if it comes back on then you know you have some other problems
 

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Discussion Starter · #3 ·
is there any other way to reset codes or do you have to use a diagnostic computer to do it?

thanks for your help
 

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some people say that you can just unhook the battery, well.........when i try it it just comes right bask on in a matter of min. if you do try the battery thing try and leave it off for at least 30 minutes. give that a try and let me know if that works for ya.
 
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Discussion Starter · #5 ·
yeah the light did just come back on so I took the positive terminal off like you said and left it off for 4 hours or so. the battery was drained when I tried to start it again. I jumped it and it ran rough for a bit then evened out to 1000rpm. no light on!

I turned off the truck and have left it on trickle charge overnight. I will see how it is in the morning and if the light comes back on any time soon but for now the long disconnect of the battery works. thanks for your help. I will keep you updated if anything changes.
 

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cool man. glad that worked for ya. if the light does come back on then hook it up to the diagnostic computer. you might have another code throwing that light on.
 

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ok Guys, The code came up because there's a problem.... most likely you have a blown plenum gasket which is either plugging up your cat converter or fouled up your o2 sensor....the code will go away on its own after the computer sees the issue is gone for a certian amount of time if it doesnt clear its still an issue. Its foolish to ignore these warning and try to clear them by just resetting the pcm by disconnecting the battery....

A.... the problem will still be there and the light will return as soon as the computer gathers enough information to recalculate your air fuel ratios which can take up to 200 miles to do now BTW because you wiped everything out... it also wont pass an emmisions test until that info it relearned (if your even in a state that does that)

B ignoring it will cause your gas mileage to go down the toliet if its a fouled 02 sensor... if the cat is plugging up it will likely leave you stranded on the side of the road when its too plugged to breath and until then your losing lots of power....

Now if you gutted your cat then this is coming up because you need to use a simulator or plug anti fouler trick to change what the downstream 02 sensor is seeing... and make sure you dont have a bosch 02 sensor they dont work well with these dodge trucks at all...
 

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Discussion Starter · #8 ·
Ok thanks for all the info guys. I have replaced the downstream O2 sensor with an NGK item. since disconnecting the battery for over an hour the engine light has stayed off and I have driven over 100ks since.

The guys at Napa told me that the O2 sensors are like light bulbs and just go out after time.

If my cat was clogged and it was affecting the O2 sensor are there sign on the sensor that would tell me? kind of like the signs on a spark plug if its running rich or lean?

is there any other way to tell if my plenum is leaking or if my cat is clogged. the truck as 170000K on it.

fuel economy is the same I think, hard to tell with crap winter fuel here in Alberta
 

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one way is to tap on it and if it rattles its bad..or if it glows at all in the dark when fully hot. also you could remove the o2 sensor before the cat and take it for a drive if it seems to run better and have more power because some of the exhaust is escaping through that hole , increasing flow than its plugging up... was the old sensor black? it should have been tan like the plugs..if either is black you likely have a blown plenum gasket which is very very common or some blowby from worn rings...of course it could also be a bad pvc valve...they are supposed to be replaced every 24,000 miles..

you can look down the throttlebody intake with a small mirror and light and look for oil laying in there... there shouldnt be any pooling ip at all... oil= bad pvc, blow by or plenum gasket
I was under the impression the light came on after the new sensor... they do fail.
 

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Discussion Starter · #10 ·
the old sensor came out tan color. kind of like rust of metal that had been exposed to high heat.

I have put another 100ks on the truck (I do long distances here into town and back!) and the light is still not on. I filled up with gas, going to check the mileage. I usually get about 450 - 500kms to engine light comes on.

I'll tap on the cat today and check over a few things. probably time for a new PVC valve just to keep up with general maintenance.

Thanks again for all your help.
 
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