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Old 04-22-2015, 10:38 AM
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P0051 & P0420 DTC's

Hello my jeep bros,
Glad to b here
I have a 03 wj 4.0L With the dtc p0051 & P0420 I replaced the air/fuel ratio bank 2 sensor 1 but the codes still pop up on the odometer when I do the system check with the key on 3 times in 5 secs. w/o cranking the engine, do I have to clear it out with a scan tool ? I did the unplugged battery for a few mins. thing and still have the codes! I luv my jeep n it's my second one but the fist was a 94 zj 4.0L I jus got rid of it n got into this 03 wj 4.0L but need it perfect to start making it look pretty like my 94 zj did. Please help. The new sensor is mopar from the dealer

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  #2  
Old 04-22-2015, 05:55 PM
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Re: P0051 & P0420 DTC's

Welcome to the garage.
The P0051 code indeed has to do with the bank 2 sensor 1. Besides the sensor, it could also be a blown fuse. Did you check that first? Its fuse #16 (15A) in the PDC under the hood. The fuse feeds the downstream sensor as well, but for some (strange) reason only the upstream sensor heater current is monitored by the PCM. If that is ok, i would first try and reset the codes and see if they come back.
The P0420 code is for the bank 1 catalyst efficiency low. It could mean that the catalyst is bad, but there are several other possibilities as well.
Ideal would be to check the readings of the O2 sensors. The 1-1 and 2-1 sensors should fluctuate a lot between 0.2-0.8V, while the downstream sensors (1-2 and 2-2) should be relatively steady. If the downstream jumps up and down as the upstream, then you will have to check for exhaust leaks, because that can influence the O2 sensor.
To monitor the O2 sensors, you will need a scanner with live data, or when you have an android phone, you only need a cheap ELM 327 bluetooth dongle from e-bay and the free Torque app.
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Old 04-23-2015, 05:14 AM
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Re: P0051 & P0420 DTC's

Thank u. I greatly appreciate it and will get on top of it ASAP!!
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Old 04-23-2015, 07:45 PM
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Re: P0051 & P0420 DTC's

So I check the fuse and I check the live data of all 4 sensors and did a smoke test to check for exhaust leaks and ALL checks out well. I also checked the resistance of the sensors connector and can't find out why I have these dtc codes and woke up to a 3rd code which is p0432 so I have that on top of p0051 & p0420 we also check the cats and they both good! IM A STUDENT AT NEW YORK AUTO MOTIVE & DESIEL INSTITUTE I have fixed everything in my beloved wj but I can't seem to b able to fix these emissions codes and don't know what to do next
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Old 04-23-2015, 09:50 PM
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Re: P0051 & P0420 DTC's

So when checking the live data from the O2 sensors, the 1-1 and 2-1 where fluctuating a lot, while the 1-2 and 2-2 where stable? The P0432 is for bank 2 catalyst low efficiency. That you have both P0420 and P0432, means that the PCM is seeing both cats to be with low efficiency. That normally means that the 1-1 and 1-2 live data should be more or less the same and the 2-1 and 2-2 as well.
You did errase the two codes and thereafter you got the three codes?
You said that you checked the catalitic converters and that they are ok, but how did you determine that?
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Old 04-24-2015, 09:55 PM
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Re: P0051 & P0420 DTC's

Well all I was able to check was the temp with the pyrometer but engine was fairly cold still but it tested over 800 degrees Fahrenheit I believe it was but I know there are more accurate **** to determine if indeed my cats are bad but I dnt have access to those kinds of tools to perform such test. I'm also a still learning student. Is there any tips u can give me to try to rectofie this issue ? The 3 codes popped rite back up after I cleard them out. Bank 2 seem to be running a lil leaner but that's all we could really see out of spec on the live data scanner. I'm afraid to have to deal with replacing a cat but I really luv this jeep and want it in optimal condition. It barely has 116k on it and I've done A TON of work on it already. Mostly all mopar oem replacements!!! Any help would be greatly appreciated
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Old 04-25-2015, 01:02 AM
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Re: P0051 & P0420 DTC's

So how where the 1-1 and 2-1 sensor outputs compared to the 1-2 and 2-2?
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Old 04-25-2015, 07:29 AM
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Re: P0051 & P0420 DTC's

I am gonna go to advanced auto parts and barrow a live data scan tool and record the exact numbers for u because to b honest wit u. I was running back and forth from my class (electronics foundations) to emissions to see what the sensors were doing and I all seemed well except that bank 2 is running leaner but like I said as soon as advanced auto parts opens today I am gonna go scan it again record the exact numbers for u. So u have a more specific idea of what is going on on my end. I want to really thank u!! I really appreciate ur help. Forums like this are incredible!!
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Old 04-25-2015, 08:41 AM
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Re: P0051 & P0420 DTC's

If you have an android phone, then you can buy a cheap ELM327 bluetooth dongle of e-bay and download the free Torque app. You can then monitor many live data and errase DTC s at any time.
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Old 03-20-2016, 05:16 PM
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P0051 & P0420 DTC's

Interesting, I have been getting the p0420 code intermittently as well.... Just ran live data and the 1-1/2-1 do jump a lot from 0.1-.8, but the 1-2/2-2 also jump around less so, but between 0.1-0.8




Guess I should check the exhaust... Of course my mechanic likely never looked at this
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Old 03-20-2016, 07:54 PM
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Re: P0051 & P0420 DTC's

When the 1-2 and 2-2 sensors jump up and down the same as the 1-1 and 2-1 sensors do, then it is a sign that the catalist is not doing its job anymore.
Your bank 1 cat seems to be the problem here.
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Old 03-20-2016, 08:03 PM
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Re: P0051 & P0420 DTC's

Quote:
Originally Posted by Frango100 View Post
When the 1-2 and 2-2 sensors jump up and down the same as the 1-1 and 2-1 sensors do, then it is a sign that the catalist is not doing its job anymore.
Your bank 1 cat seems to be the problem here.

Thanks for the info, this has been bugging me since I picked this 09 Overland up last year
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