P0138 & P2097 OBDII Codes

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  #1  
Old 08-06-10, 02:28 PM
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P0138 & P2097 OBDII Codes

The "Check Engine" light on my 2005 Dodge Caravan came on a four weeks ago. I connected a scanner and pulled code P0138 (O2 sensor circuit high voltage - bank 1, sensor 2). Hoping it was a transient error, I cleared the code. The engine light didn't come back on until two weeks ago. The same code came back on and I cleared it again. After a few days the light came back on again only this time I had two codes - P0138 and P2097 (Post Catalyst Fuel Trim System Too Rich Bank 1).

I was planning on changing out the O2 sensor until the second code (P2097) popped up, but now I'm not sure if I might have a different problem. Do you think I have a single problem causing both codes and what do you think might be the cause? Could it still be the O2 sensor? I've also heard that the spark plugs could cause this but I have platinum plugs installed with less than 15,000 miles on them.
 
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  #2  
Old 08-07-10, 07:36 PM
Join Date: Jul 2009
Location: Washington State
Posts: 312
Without long term fuel trim info a tough one to diag over the net.The codes you are getting can be caused by one of four things.
Small misfire on bank one that doesn't cross the ECU's threshold for a misfire code thus too much fuel going to the exh for the cat to handle.
A wiring or sensor issue causing the pre/post cat readings to cross the threshold for a MIL (check engine light)
Cat itself bad.
Faulty ECU
Being the high voltage is the primary code on the post cat sensor I'd start with a close inspection of the plug ins and wiring going all the way to the ECU,Also clean all contacts with electrical contact cleaner only. (This code is caused by more than 5volt ref voltage being received by ECU since it only sends 5 to it for the sensor but sends 12 to its heater)
It is possible for the sensor to have an internal short but unlikely the cause of this.
15 K isn't a lot of miles on plat plugs but I'd also at least pull the plugs and wires replace wires and inspect the plugs clean and regap.
Have the feeling you are dealing with a slight misfire and it's taking about 200 miles to show up on emission protocols before tossing the light.
 
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