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Unread 10-01-2014, 10:51 AM   #1
billd
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New Exhaust=Code 21

Hi! I have a 95 Gr. Cherokee with a 5.2
I just put a new cat.converter and a muffler on and now after 5 minutes of
driving the Check engine light comes on. It really ran crappy immediately after doing the install but has since smoothed out somewhat.
The code I pulled is 21 for the oxygen sensor.
Don't quite get how components downstream can affect the sensor?
How can I fix this? Thoughts?
Will it hurt it to drive it this way?

Thanx!!

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Unread 10-01-2014, 11:04 AM   #2
HighLonesome
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You will burn more gas.

You did the install or a shop?
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Unread 10-01-2014, 11:06 AM   #3
billd
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I did the work.
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Unread 10-01-2014, 11:10 AM   #4
HighLonesome
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Code 21 is an electrical problem. Last time I saw that code it was a broken wire.

Did you reset the computer?
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Unread 10-01-2014, 11:17 AM   #5
billd
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Yes, being a 95 I had to undo the neg. battery cable. That worked and the code is gone. I haven't driven it yet to see if the code will return, however. Getting ready to do that now. The old cat. conv. was toast and all broken down inside. I had a 13" Flowmaster muffler on it and replaced that with a 18" OEM sized Walker muffler. It really ran like crap during the test drive after doing the work but has smoothed out considerably.
Gonna go test drive it again now.
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Unread 10-01-2014, 11:22 AM   #6
HighLonesome
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Mine acted like that when a wire was broken. Code always came back after a couple minutes. Hopefully yours will stay gone.

If it does come back, I guess I would check the wiring first. After that the obvious...replace the sensor. There is a heater inside the 02 sensor. If the heater opens electrically, that will cause the code.
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Unread 10-01-2014, 11:35 AM   #7
billd
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Yeah, the code came back after about 2 miles. It's weird because if I turn the engine off and restart the code is gone until I drive a few miles. Don't get it as before the new components ...no light. And I was no where near the O2 sensor. I looked at it briefly and there was nothing obvious with the wires from the sensor. I'm wondering if she doesn't like the new muffler. Maybe a bit more back pressure could be causing this. She has 180,000 on the clock and has never given me this kind of grief. I guess I'll try replacing the sensor. It's gonna be a bear, though, as it's probably been in there since 95.
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Unread 10-02-2014, 03:28 AM   #8
ZeeJay1997
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Quote:
Originally Posted by billd View Post
\ it's probably been in there since 95.
more the reason to change it. get an ntk brand sensor. others may cause problems.
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Unread 10-02-2014, 07:14 PM   #9
billd
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Yeah....I know. All I gotta do now is figure a way to get it out. I've had round 1 with it already.
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Unread 10-02-2014, 07:21 PM   #10
ZeeJay1997
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i had good luck with remove it while the pipe is hot.
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