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Unread 07-06-2007, 03:16 PM   #1
cromero
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1996 XJ Cherokee 
 
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Location: Baton Rouge, LA
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fault codes 351 and 420 need help

fault code 351: Ignition Coil A Primary/Secondary Circuit
Peak primary circuit current not achieved with maximum dwell time.

and

fault code 420: Catalyst System Efficiency Below Threshold (Bank 1)
Catalyst 1/1 efficiency below required level.


what's wrong and what needs to be done?

thanx.

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Unread 07-06-2007, 06:06 PM   #2
regpugeda
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fault code 420

I just have the same diagnostic code on my '96 Jeep GC Ltd. few weeks ago. Dealer put in new catalytic converter as per E-22 emission recall. Check engine light and code disappear and its running fine.
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Unread 07-06-2007, 06:41 PM   #3
rm2001wj
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At least give us the model year and engine. Not all Grand Cherokees are the same.

Probably you have a 99 - 04 which is a WJ. Coil A is the coil for cylinder #1 so I guess you have a 4.7L engine, and there is a problem with that coil, and it needs to be replaced. If I'm correct about the engine size, then P0420 means the efficiency of the minicat on the driver side of the engine is too low and it needs to be replaced.

A bad coil on #1 plug could mean unburned gas is getting into the minicat on the driver side and causing the P0420. Fix the coil problem first, erase the codes, and then drive for a while to see if the P0420 returns.
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Unread 07-06-2007, 09:45 PM   #4
rxl
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What if all you have is a code 420. Would that be the bank one o2 sensor needs replaced??
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Unread 07-06-2007, 10:24 PM   #5
rm2001wj
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Quote:
Originally Posted by rxl
What if all you have is a code 420. Would that be the bank one o2 sensor needs replaced??
Since the downstream O2 sensor signal is used to determine the cat efficiency, you could hope that the problem is with the sensor and not the cat. However, when the cat efficiency drops too low, the downstream sensor produces a signal that closely duplicates the upstream sensor signal. That duplicating behavior would be highly unlikely if the downstream sensor was boogered up.
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Unread 07-06-2007, 10:29 PM   #6
rxl
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Boogered, lol. So what your saying is the problem is more likely to be the upstream sensor ?? I ask because I have the same code and my cat was new about 9 months ago.
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I bought "MY JEEP" for my wife
I bought "MY OTHER JEEP" for my daughter [she sold it]
I finally bought one for me

Canadian Jeep Club Member #7

99 GC limited
4.7 Quadradrive


97 TJ Sport
4.0 5 speed

99TJ Sahara
4.0 Auto

Sold to a life of blacktop
94 ZJ Limited
I6 Quadratrac
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Unread 07-07-2007, 08:32 AM   #7
rm2001wj
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Quote:
Originally Posted by rxl
Boogered, lol. So what your saying is the problem is more likely to be the upstream sensor ?? I ask because I have the same code and my cat was new about 9 months ago.
No, I wouldn't say that. A problem with the upstream sensor would cause a different code. Something else is going on.

Does your 99 WJ have the California emissions exhaust system composed of two minicats along with a larger cat in front of the muffler? Or, does it have a simple Federal system consisting of a single cat in front of the muffler?

Also, what cat did you replace and why did you do it? Was the replacement OEM or an after market product that might be called a "high flow" cat?
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Unread 07-07-2007, 11:04 PM   #8
rxl
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Looks oem but i'm not sure. It was one of the things I negotiated in a purchase agreement. Thanks for the info. Seems like the cat is the problem with the 420 code. (catalyst 1/1 below efficiency below required level)
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99 GC limited
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4.0 5 speed

99TJ Sahara
4.0 Auto

Sold to a life of blacktop
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Unread 07-09-2007, 07:40 PM   #9
cromero
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the replies here are great. it's a 96 GC with the 4.0 l engine. i have already replaced the coil, wires, plugs and dist cap. i also replaced the upstream o2 sensor as well as the fuel pump and filter. Also remove the fuel rail and injevtors and did major clean up and replaced the o-rings. i did clear the codes and they came back. I tend to believe the cat converter is the problem with the codes and plan to do the dealer thing next. i did have the recall done on it about 4 months ago, so that may have caused the prob. Now i'm fighting something new. the GC periodically stalls and won't start after starting from cooldown periods. This problem arose after replacing fuel pump. It only starts after i depressurized the fuel system line at the fuel rail pressure check point. any help or ideas?
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Unread 10-27-2009, 04:10 PM   #10
ta3834bbl
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I know this is an old thread, but my '96GC is showing a po132 code and p0351 code. I have replaced the cap, rotor, plugs, and coil, but not the wires. I have also replaced both O2 sensors but not in the last few months. I don't know why I am getting the Coil A primary/secondary fault, could it be the wires? And the O2 sensor says hi voltage. What would cause this? Any help would be appreciated. You can email me at todd@moparworld.com My wife thanks you .
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Unread 10-27-2009, 11:05 PM   #11
rooster51
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W/ the P0351, yes, replace the wires. If that dont work try the camshaft positioning sensor, if that dont work... its more than likely a bad/dying PCM.
Ive come to learn from personal experiance that P0351 is french for replace/repair PCM.
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Unread 10-28-2009, 09:45 PM   #12
ta3834bbl
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Thanks for the reply, I will replace the wire set, the front o2 sensor , and go from there.
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Unread 03-02-2010, 10:43 AM   #13
ta3834bbl
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It's still there but the dying is getting worse and 2 times now it was really hard to start. To recap : I have replaced both 02 sensors, the coil, the TPS, idle speed sol, crank pos sensor 2 times, and the cam sensor (dist pickup coil ), wires, plugs. I keep getting the p0123 code all the time, but now I'm am back to the p0351 code also. I did the wiggle test at the pcm and it stumbles so I think I may be on to something. What would you recommend to clean / cure bad pcm connections, or will I be looking at repairing the harness/connector. I realize you can't , nor can I yet , see what my problem is but is it common to have bad wiring or more common to have filthy corroded connections? Thanks. '96 GC 4.0 Orvis Edition.
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Unread 03-02-2010, 11:21 PM   #14
rooster51
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Quote:
Originally Posted by ta3834bbl View Post
It's still there but the dying is getting worse and 2 times now it was really hard to start. To recap : I have replaced both 02 sensors, the coil, the TPS, idle speed sol, crank pos sensor 2 times, and the cam sensor (dist pickup coil ), wires, plugs. I keep getting the p0123 code all the time, but now I'm am back to the p0351 code also. I did the wiggle test at the pcm and it stumbles so I think I may be on to something. What would you recommend to clean / cure bad pcm connections, or will I be looking at repairing the harness/connector. I realize you can't , nor can I yet , see what my problem is but is it common to have bad wiring or more common to have filthy corroded connections? Thanks. '96 GC 4.0 Orvis Edition.
Just as likely to have bad capacitors in the pcm. You can try cleaning the connections then put dialectric (???) grease in every pinhole in the plug. make sure your pcm plugs are secure. Probably a good idea to contemplate either a brain trasplant or brain surgery( replacing the capacitors) on the pcm.
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