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Threw a Code: po138


Old 12-18-2005, 09:32 PM
SLT360 is offline
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Default Threw a Code: po138

My Baby, 99 SLT 5.9 4x4 1500 threw the code p0138....Basicly rear oxygen sensor high voltage. After searching the forum i found a few old threads dealing with either cleaning it or preferable replaceing with a mopar or similar sensor. 2nd time its thrown it in the past week and i have cleared it both times.

1. Will running for a week with this damage anything?
2. What EXACTLY does this mean.....high voltage to a sensor doesnt really mean anything to me?
3. Affect gas mileage....not that it matters with these babies
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Old 12-18-2005, 10:54 PM
Socha_62 is offline
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Default RE: Threw a Code: po138

It won't hurt anything running it like that. If its the rear sensor its either actually bad itself, or your cat isn't working right.

High voltage just means its getting a reading from it out of the normal operating range. It gets this higher reading because of what I just said, sensors bad or cat isn't working right
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Old 12-18-2005, 11:23 PM
shott8283 is offline
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Default RE: Threw a Code: po138

you can try taking the aft o2 sensor out and cleaning it really good... becarefull though... they are delicate..just wipe it down and maybe spray it with some carb cleaner... LIGHTLEY spray it and wipe it down and let it airdry overnight.... make sure its screwed back in nice and snug and hook it make up..also make sure the plug is clean too..on both ends... make sure theres no dust... but with that code it prolyl means you need a new one... too high voltage.. prolly shorted out or malfuntioned... when i went to change mine out .. it cost me 120 bux for a brand new mopar one... reason being is that if you get the universal ones..they tend to not work right and throw codes and **** you off... i hate seeing my CEL on... if you clean your original one.. itll help to blow it out with some compressed air..also if you put the new one in and see if the CEL comes back on...if it doesnt..throw the old one back in and see if it comes back... good way to make sure you spent 120 or so bones good...
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Old 12-18-2005, 11:59 PM
SLT360 is offline
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Default RE: Threw a Code: po138

thanx, i dug up a old troubleshooting book and it said the exact same thing you guys did. so i think ill just replace it this weekend....i assume i have to go through a dealership to get a mopar sensor?
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Old 12-19-2005, 12:29 AM
bamory is offline
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Location: OHIO
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Default RE: Threw a Code: po138

Mine threw the same code, I took it out and used Carb cleaner and a toothbrush to clean it (inside the grooves were carboned up), that was 15,000 miles ago, not saying you will get that much outta yours, but it can keep the 60.00 in your pocket longer
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Old 11-13-2011, 06:57 PM
larryb09 is offline
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what would cause my 5.2 liter '98 ram 1500 4x4 to idle high up and down on start up and while driving?
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Old 11-13-2011, 07:27 PM
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Bad IAC motor, or, failing TPS, or Failing O2. Does it always do it? only when warm? Just till it warms up a bit??
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Old 11-14-2011, 01:34 PM
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Thank you Hey You! These are what I was kind of leaning towards.
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Old 10-30-2012, 10:35 AM
hemi 2500
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so does anyone know what bank 1 sensor 2 is on a ram 2500 2003, it didnt say upstream or downstream .
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Old 10-30-2012, 11:19 AM
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bank one- drivers side four cylinders.. sensor two- behind the first one, aka 'downwind'..

if you're running a fed emissions rig, sensor 2 is the downwind, period (for both sides)
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