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o2 sensor short to power


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The signal wire from my o2 sensor has a perfect 5volts at all times, even when the key is in my pocket. Anyone ever heard of such a problem?

 

this occurs with and without the sensor plugged in, truck running, key on, truck off, key on, or truck off, key off. the grey signal wire ALWAYS has 5V

 

and also does anyone know if the heater circuit for the o2 sensor is supposed to run off 12v?

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which vehicle are you refering to? What controller are you running? Typically the heater runs off 12 V. That 5v you see may be a diagnostic voltage if you are looking at a non renix controller (not sure what renix does for that), but it should be off when the key is off, unless your controller isn't shutting down?

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You'll get the 5V signal when first started (closed loop) until transition to open loop, but it definately shouldn't be there w. IGN off. Why are you asking? Installing an A/F meter?

 

And the heater circuit on a 4-wire O2 sensor is run by IGN-switched 12V.

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You'll get the 5V signal when first started (closed loop) until transition to open loop, but it definately shouldn't be there w. IGN off. Why are you asking? Installing an A/F meter?

 

And the heater circuit on a 4-wire O2 sensor is run by IGN-switched 12V.

One of us has our loops confoozled. I have always thought that the initial, warm-up mode was "open-loop" mode because there IS no loop -- the sensors don't provide data to the ECU. Once warmed up, I thought the normal operating mode was "closed-loop" because the sensors are "in the loop," hence ==> closed loop.

 

Yes? No? Maybe?

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You'll get the 5V signal when first started (closed loop) until transition to open loop, but it definately shouldn't be there w. IGN off. Why are you asking? Installing an A/F meter?

 

And the heater circuit on a 4-wire O2 sensor is run by IGN-switched 12V.

thanks for that, i was hoping someone would have my magical answer i needed!

 

the first part sounds like my issue. but the heater circuit in the sensor is kerfuct so it's not achieving closed loop and thus i never saw the signal change. *i think you have the loops backwards*

 

sorry, i'm a renix guy! forgot to mention that. guess i'll throw a sensor at it tomorrow and go from there.

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One of us has our loops confoozled. I have always thought that the initial, warm-up mode was "open-loop" mode because there IS no loop -- the sensors don't provide data to the ECU. Once warmed up, I thought the normal operating mode was "closed-loop" because the sensors are "in the loop," hence ==> closed loop.

 

Yes? No? Maybe?

i don't know what the reasoning is on it but yes, you are correct in thinking open loop is warm-up cycle.

 

my truck never achieved closed loop today so i guess i never saw the sensor come online.

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One of us has our loops confoozled. I have always thought that the initial, warm-up mode was "open-loop" mode because there IS no loop -- the sensors don't provide data to the ECU. Once warmed up, I thought the normal operating mode was "closed-loop" because the sensors are "in the loop," hence ==> closed loop. Yes? No? Maybe?

 

IB the one to be confoozled (nice word). :D Just flip what I said 180 - I was editing it when you replied. :nuts:

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still though, :bowdown: thanks for the idea... that never even BEGAN to cross my mind, i figured my ECU was through-dealin'

 

the theory-of-operation i found in the FSM made no mention of that but it makes sense and they love to omit things :popcorn:

 

thanks horn, you've always got good thoughts for me. image_209027.gif

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thanks guys, just to follow up in-case of a future search,

 

o2 sensor has 5v on the sensor wire until the truck reaches closed loop and then it switches on, bouncing back and forth.

 

also,

the truck will NOT enter closed loop without a working heater in the o2 sensor (at least mine wouldn't) and the coolant temp must be over 85* C (185* F)

 

passed emissions today with flying colors, putting damn near clean air out the tail-pipe. :banana:

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this occurs with and without the sensor plugged in, truck running, key on, truck off, key on, or truck off, key off. the grey signal wire ALWAYS has 5V

 

 

Wireless electricity is some crazy stuff man. Might want to get some scientists on that...

 

I'm guessing that you mean not threaded into the exhaust. But its late and it took me entirely too long to figure that out.

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