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Old 12-22-2017, 07:17 PM   #1
Join Date: Oct 2017
Location: Ashland City
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02 voltage question

is there any reason for voltage to drop to 0 on an 02 sensor. ive been working on a p0300 and was watching some LD tonight and found that when my truck starts to miss the voltage is at 0 on B2 S2. when missing stops the voltage is at .115. witch is low I think. the other 02's bounce around at .750

does this data tell me its a bad 02 or am I chasing something else

vacuum is rock steady at 19
fuel pressure is 52 cold and 62 at idle, fuel pressure drop is 2 to 4 lbs after 5 or more minutes
have not done compression check

long term fuel trim B2 cold start is -30 (rich condition correct?) once warm runs around -10 it never goes 0 or positive. there is improvement when the peddle is pressed. the other st and lt bounce around but spend more time in the neg range

I know its a lot of info just trying to provide all the info I can.

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Old 12-22-2017, 07:45 PM   #2
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The voltage should never reach 0 most times that will set a code. You may be dealing with a bad 02 sensor for sure. Does this happen on startup only and how often. You could try starting the truck sensor unplugged and see if it still misses the pcm will run on a default voltage so it should run ok.
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Old 12-22-2017, 08:01 PM   #3
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Agree, zero voltage indicates a problem. Most likely a bad o2s. You could swap o2s and see if the problem follows.
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