CEL and diagnosis
Record Breaker
Joined: Dec 2018
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Yup, found this in the manual "The 8.0L V-10 engine uses two oxygen sensors, one in each exhaust down pipe." ...
But with that said, you mentioned these wouldn't trigger a CEL, which then brings me back to what the mechanic said, in that is was probably caused by the evac canister.
The question now is, why did I get the following code when turning the ignition key and the following description?
12 - 21 - 21 - 55
Did it twice and the same thing - got a 21 twice both times. If my research was correct, 21 indicates the following: 21** Problem w/ oxygen sensor signal circuit. Sensor voltage to computer not fluctuating. (** means it will trip the Check Engine Light).
But with that said, you mentioned these wouldn't trigger a CEL, which then brings me back to what the mechanic said, in that is was probably caused by the evac canister.
The question now is, why did I get the following code when turning the ignition key and the following description?
12 - 21 - 21 - 55
Did it twice and the same thing - got a 21 twice both times. If my research was correct, 21 indicates the following: 21** Problem w/ oxygen sensor signal circuit. Sensor voltage to computer not fluctuating. (** means it will trip the Check Engine Light).
As a WAG I'd say you get code 21 twice because both 02 sensors have a problem. You can change both but personally, I'm cheap and try to avoid throwing parts at a problem and rather spend more time troubleshooting. Make sure the O2 heaters work (they are always on unlike in later years so it should be easy) and check what voltages appear on the sensor signal wires with/without the sensor connected. See 8W-30-39 in the FSM for wiring details.
Grand Champion
Joined: Feb 2015
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The key dance codes are general faults, If you want details you need to get the "P" codes with a code reader. But there is a problem with the pcm not seeing any change in the 02 sensor return voltage. Take it to a autozone or any of the parts stores that will read your codes for free and go from there.
Administrator
Joined: Apr 2010
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From: Clayton MI
The key dance codes are general faults, If you want details you need to get the "P" codes with a code reader. But there is a problem with the pcm not seeing any change in the 02 sensor return voltage. Take it to a autozone or any of the parts stores that will read your codes for free and go from there.
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Professional
Joined: Jan 2019
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From: Upstate New York
I'll have to check them out anyway once I can catch a break in the weather ...
Last edited by nyrainman; Feb 1, 2021 at 02:44 PM.
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Professional
Joined: Jan 2019
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From: Upstate New York
Not sure exactly how to do that but will look more into it. My son-in-law can probably help me with this once the weather breaks a little. We're expecting another 12" of snow over the next couple days. YIKES ... but I do have the diagram from the manual you mentioned - thanks.
Administrator
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From: Clayton MI
If the PCM is whining about voltage not switching..... they are bad. There are other codes for other failure modes.
Registered User
Joined: Jan 2021
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From: Florence SC
Excuse me for jumping into this thread,I could not figure out how to pose a question .Is there another scan tool that you can use to adjust fuel timing besides the Snap on 2500 ? Thank you for any input . Georgeharry
Record Breaker
Joined: Dec 2018
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Chrysler DRBIII, OTC Genisys (and the rebranded derivates) are the ones I know of. However there is a procedure in the FSM which brings it close enough.
