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Unread 02-17-2014, 06:04 PM   #1
Mpaule
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Check Engine Light

Have a 98 Wrangler, 2.5l, 4 cyl. 98K miles. We are new to Jeeps. This issue seems to be common problem in jeep world, but here goes my scenario: Engine would essentially "choke up" and slow down to a stop on me. Initial reaction was trans, but upon inspection trans is in good shape. So first thing a local aftermarket jeep shop did was replace cat conv (aftermarket), along with muffler and tail pipe. Little rusty down there. Power issue seemed to improve greatly and bogging down appears eliminated, however, CEL came on a few days later. With code in hand, I then replaced both o2 sensors (aftermarket), only to have CEL return two days later. Then I replaced spark plugs and connectors, with CEL returning. Then gas cap was replaced. CEL returned. Now I determined it was time for an authorized jeep dealer to figure it out. Dealer replaced a cracked exhaust manifold. Jeep ran better, but CEL returned two days later. Dealer then located an opening in exhaust pipe left when cat conv was replaced and welded it closed. CEL returned. While I must admit with each of these fixes, my Jeep's performance and/or noise emission has improved, I cannot seem to find root cause of CEL returning. Anyone out there have any thoughts? Scratching my head (along with dealer I think).
I am not able to do the key trick on the Jeep to get a code. I have been to AutoZone to get P0420 code, but it relates to cat conv, O2 sensors, or misfirings all of which I "think" I have corrected. I took this issue to dealer thinking they would be the jeep experts as far as code determination and trouble shooting all possible causes.
Any insight would be appreciated.
Update at Feb 21: No solutions. Back to Dealer on Tuesday. Not a big Jeep fan at this point. There just aren't that many parts on a Jeep, and it seems this is a common occurrence to Jeeps.
Update at Feb 28th Took to dealer who stated that it must be O2 sensors - even though I replaced these a few weeks back they said Jeep must have factory O2 sensors - so we replaced them. Test drove for a day after they were replaced. I then picked up Jeep today, and CEL returns this evening. So its not the O2 sensors - factory or aftermarket. I am open from any advice from the experts out there.
UPDATE ON 4/10/2013 - APPEARS THAT AN INTAKE AIR TEMPERATURE SENSOR - $33.00 PART IS KEEPING CEL FROM RETURNING THUS FAR. DEALER COULDNT DIAGNOSE THIS. AFTERMARKET JEEP SHOP DID.
UPDATE ON 5/28/2013 - FINAL FIX ENDED UP HAVING TO MOVE O2 SENSORS FURTHER AWAY FROM CAT CONVERTER. THEY WERE GETTING TO HOT. CAT WAS AN AFTERMARKET PRODUCT - MFG DID NOT PROVIDE THIS INFO UNTIL AFTER WE CALLED LOOKING FOR SOLUTIONS. CEL HAS NOT RETURNED FOR WEEKS. HOPE THIS HELPS SOME ONE ELSE OUT THERE HAVING A CEL ISSUE.


Last edited by Mpaule; 05-28-2014 at 06:06 AM.. Reason: Provide Update
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Unread 02-17-2014, 08:20 PM   #2
WhiteMtnJeep
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What code are you getting?
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Unread 02-17-2014, 08:34 PM   #3
catmechanic
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Turn the key on-off-on-off-on without starting it. A code (Pxxxx- x being numbers) will show up on the odometer display. Google "jeep code Pxxxx" and you should get some pretty solid returns and starting points.
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Unread 02-17-2014, 08:51 PM   #4
WhiteMtnJeep
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Key trick does not work on a 98. That only works on OBDII, 98 is OBDI. Go to autozone and they will read it for you.
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Unread 02-17-2014, 08:56 PM   #5
99TJSahara
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Quote:
Originally Posted by WhiteMtnJeep
Key trick does not work on a 98. That only works on OBDII, 98 is OBDI. Go to autozone and they will read it for you.
98 is OBDII, everything 96+ is OBDII
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Unread 02-17-2014, 09:02 PM   #6
Wheelin98TJ
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Quote:
Originally Posted by WhiteMtnJeep View Post
Key trick does not work on a 98. That only works on OBDII, 98 is OBDI. Go to autozone and they will read it for you.
You are correct, the key trick does not work on '98 model TJs, but as 99TJSahara mentioned, '98 is OBD II.

The key trick does not work on '98 models for some other reason.
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Unread 02-18-2014, 01:40 AM   #7
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Quote:
Originally Posted by Wheelin98TJ View Post
You are correct, the key trick does not work on '98 model TJs, but as 99TJSahara mentioned, '98 is OBD II.

The key trick does not work on '98 models for some other reason.
It also doesn't work on 1999 and 2000 model TJ's...
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Unread 02-18-2014, 02:19 AM   #8
trickydick
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Another option is that you could order an ELM327 obdII reader off ebay and download the torque app for your smartphone and for roughly 25$ you can read your own obdII codes and clear them as needed. It will also let you look up the common causes of these codes on the internet with your phone. It will also work for any other vehicles you have.
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Unread 02-18-2014, 05:57 AM   #9
Mpaule
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Code from Autozone was P0420. I cannot do the key trick on this jeep for some reason. Not sure what codes dealer was reading. Thanks for inquiry.
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Unread 02-18-2014, 06:10 AM   #10
SomeBeach
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I would take time and check the O2 sensors connectors for corrosion or bad connections and cracked wires beyond the sensor's pigtail. The ECU is probably not getting good readings from the sensors and that is messing with your air/fuel mix causing the bogging and stalling.
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Unread 02-18-2014, 06:50 AM   #11
Mpaule
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Check Engine Light

[QUOTE=SomeBeach;20474145]I would take time and check the O2 sensors connectors for corrosion or bad connections and cracked wires beyond the sensor's pigtail. The ECU is probably not getting good readings from the sensors and that is messing with your air/fuel mix causing the bogging and stalling.
Thanks for reply and interest. I had replaced the O2 sensors but with aftermarket, not Jeep branded product. Probably retracing my install and wire connections would be a worthwhile start. The bogging down has seem to be eliminated after cat conv and exhaust manifold was replaced. Thanks again. Getting curious if electrical system malfunction could be cause of CEL?
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Unread 02-18-2014, 08:35 AM   #12
SomeBeach
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If you have a cracked/bare wire that connects to an O2 sensor and the ECU is getting bad or no readings, that will give you the Check Engine lights and codes.
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Unread 02-18-2014, 09:16 AM   #13
Wheelin98TJ
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Quote:
Originally Posted by Knuckelhead View Post
It also doesn't work on 1999 and 2000 model TJ's...
Correct, I just didn't mention it because its not relevant to this thread.

Thanks again for pointing this out previously so I could add this info the FAQ.
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Unread 02-18-2014, 06:21 PM   #14
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Quote:
Originally Posted by SomeBeach View Post
If you have a cracked/bare wire that connects to an O2 sensor and the ECU is getting bad or no readings, that will give you the Check Engine lights and codes.
Keep in mind that 1997-2006 TJ's don't have an ECM (no mention of it in the FSM). They have a Powertrain Control modal (PCM)... HTH
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Unread 02-18-2014, 06:22 PM   #15
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Originally Posted by Wheelin98TJ View Post
Thanks again for pointing this out previously so I could add this info the FAQ.
You're welcome...
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