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  #1  
Old January 7th, 2019, 14:03
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Feedback voltage from tps into o2 sensor?

Renix 4.0
I was out in the garage messing around with my engine scanner and noticed something strange.
With engine off key on i was watching the tps signal while i was pushing the gas pedal.
At the same time i had the o2 circuit pulled up on split screen and noticed that when i pushed the gas the o2 feed would go up a few 10ths of a volt....
Weird right?
Is this something normal or should i start digging into the harness and see if ive got a short between the two circuits?
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Old January 7th, 2019, 15:44
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Re: Feedback voltage from tps into o2 sensor?

What kinda vehicle are you working on ?
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Old January 7th, 2019, 15:54
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Re: Feedback voltage from tps into o2 sensor?

89 xj 4.0
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Old January 7th, 2019, 15:55
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Re: Feedback voltage from tps into o2 sensor?

Where are the resident renix experts?
Cruiser....590....ect.
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Old January 7th, 2019, 15:56
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Re: Feedback voltage from tps into o2 sensor?

Might be back feed from the ground circuit. Ohm your TPS ground to battery negative.
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Old January 7th, 2019, 17:53
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Re: Feedback voltage from tps into o2 sensor?

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Originally Posted by 8Mud View Post
Might be back feed from the ground circuit. Ohm your TPS ground to battery negative.

That's my guess as well. Have a look at the ground to the block where the oil dipstick mounts. I believe all the sensor ground converge there.


http://cruiser54.com/?p=19
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Old January 9th, 2019, 03:44
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Re: Feedback voltage from tps into o2 sensor?

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Originally Posted by lawsoncl View Post
That's my guess as well. Have a look at the ground to the block where the oil dipstick mounts. I believe all the sensor ground converge there.


http://cruiser54.com/?p=19
That's a good one as is this one. http://cruiser54.com/?p=44
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Old January 9th, 2019, 03:59
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Re: Feedback voltage from tps into o2 sensor?

I wouldn't be surprised to see this. The voltage amount you are seeing is most likely just normal leakage and the source is a capacitance somewhere in the system.

When you power down, most circuits go into a high Z state. It takes a while for the voltages to bleed off all the way. Even then, things like a keep alive voltage for internal clocks on the radio can leak back through quite unexpected paths. We deal with this frequently in the testing I do on satellites.

This is not the droid you are looking for.

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Old January 9th, 2019, 16:31
lawsoncl lawsoncl is offline
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Re: Feedback voltage from tps into o2 sensor?

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Originally Posted by old_man View Post
I wouldn't be surprised to see this. The voltage amount you are seeing is most likely just normal leakage and the source is a capacitance somewhere in the system.

When you power down, most circuits go into a high Z state. It takes a while for the voltages to bleed off all the way. Even then, things like a keep alive voltage for internal clocks on the radio can leak back through quite unexpected paths. We deal with this frequently in the testing I do on satellites.

This is not the droid you are looking for.




"Engine Off, Key on", so sensors are still powered.
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