Problem diagnosing P0153 code

Salek_714

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Original poster
Joined
Jul 8, 2020
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35
Location
Orange county, CA
Hello hopefully someone here can guide me the right way! I'm currently diagnosing p0153 for slow response from sensor bank 2/1. I replaced the sensor a few weeks ago since I thought that would fix the problem. I checked the code and freeze frame data and found that my fuel trims when the code was set off were all okay which is wierd cause usually a bad sensor/circuit would cause bad fuel trims. Iv been watching the fuel trims for weeks and the trims for bank 1 & 2 are perfect even with the check engine light on.

I finally decided to start diagnosing. Mitchell pro demand says I should see reference voltage from harness side when the sensor disconnected of 4.5v to 5v. I found 4.2v volts on both up stream sensors. Mitchell says to check all the wiring from the sensor to the pcm and grounds if all is okay it says replace the pcm. While checking the resistance in the wiring I found no faults and my ground to my sensor is okay. At this point I feel like I have a bad pcm.

I've deleted the code several times and after a few drive cycles I get the code back with no symptoms that indicate I have a fault anywhere. Sadly I don't have a oscilloscope to see my waves from the sensors which maybe would be helpful but at this point that I checked all the wiring and replaced the sensor with the NTK one I feel like I'm ganna have pcm issue.

Something to note is that the pcm had already been replaced from the previous owner and I didn't notice till I actually looked at it and it looked fairly new and the tag says, the new pcm isn't even 8 months old! So idk were they bought it from, they could have probably have bought it from ebay and I don't know! Hopefully someone can put there input on this issue before I drop some money on a pcm thanks!
 
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Reactions: Wranglerfix
@Wranglerfix is the PCM guy around here so he can probably chime in in regards to how to rule out your PCM for sure. You forgot though to include the year and engine of your TJ.

My experience with these O2 sensor codes is that often times if they don't go away they are related to a short in the wiring. Unfortunately sometimes those shorts require dismantling the wiring harness and inspecting things very, very thoroughly.
 
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It's a 2005 jeep wrangler 4.0. like I said there are no symptoms. Iv already inspection all the wiring for cuts and frays and tested the wiring with an ohm meter and did a wiggle test in the wiring.
 
Have you checked your exhaust for leaks? Some have to go as far as smoking the exhaust to find the leaks.
 
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Reactions: RMETeeJay
I was thinking about doing it but if I had an exhaust leak my fuel trims would not be stable. At idle and driving the fuel trims are perfect. They stay very close to zero, long term & short term.