Can't get Oxygen Sensor reading

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Can't get Oxygen Sensor reading

Postby nickyy » Wed Jun 04, 2014 11:23 pm

I've connected channel A via an intrusive clip to an 02 sensor's (non-heated) wire. It's a probe with a point at the end that cuts through the wire. The probe has a connection that I've been told can be used for ground (I guess the BNC connector carries its own ground).

1) I need to know the recommended wire hookups from the PICO to the 02 sensor.
2) I need to know the recommended software settings (I've played around with 500 ms/div, x1, 50s) but my waveform reception has been hit or miss.

I've been able to see a slow-moving waveform between 1 and 0 volts (which sounds about right) but the waveform is clustered too tightly for me to examine it.

Please advise.
Thanks,
Nick
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Re: Can't get Oxygen Sensor reading

Postby volrem » Thu Jun 05, 2014 2:16 pm

From Pico menu go to Automotive -> Sensors -> Lambda -> Zirconia and you get bit info and startup settings.

Also post a measured file so we can give more suggestions.

500 ms/div should be ok for a start.
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Re: Can't get Oxygen Sensor reading

Postby Robski » Thu Jun 05, 2014 3:20 pm

The probe has a connection that I've been told can be used for ground (I guess the BNC connector carries its own ground).

Elaborate ??
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Re: Can't get Oxygen Sensor reading

Postby nickyy » Fri Jun 13, 2014 6:13 pm

The test lead is a red wire with a black "Y" connection in the middle going to a BNC. I assume the red goes to the black wire on a 4-wire sensor and the black one goes to the ground. Is this correct?
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Re: Can't get Oxygen Sensor reading

Postby nickyy » Fri Jun 13, 2014 6:20 pm

Here's the file
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honda accord.psdata
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Re: Can't get Oxygen Sensor reading

Postby Robski » Fri Jun 13, 2014 7:06 pm

nickyy wrote:The test lead is a red wire with a black "Y" connection in the middle going to a BNC. I assume the red goes to the black wire on a 4-wire sensor and the black one goes to the ground. Is this correct?

Yes....... black = ground, red = signal.

If you're just using 1 CH to test the O2 (Zirconia I presume?) then for a cleaner signal you can use the sensor ground as long as it's not a floating one !
Last edited by Robski on Wed Jun 18, 2014 4:12 pm, edited 1 time in total.
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Re: Can't get Oxygen Sensor reading

Postby nickyy » Wed Jun 18, 2014 4:08 pm

Then why is my waveform so screwy looking? It's the same on multiple vehicles, so I don't think it's the way I connect to the sensor; rather, it's probably a software configuration error. Please advise.
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Re: Can't get Oxygen Sensor reading

Postby Robski » Wed Jun 18, 2014 4:13 pm

when I get a minute I'll look at your capture again .........

You have 11+V amplitude, are you sure you're grounded at a good ground ?

Are you sure you're stabbing the correct wire ?

Can you try using breakout leads & leave the signal disconnected & test the signal straight from the O2 ?
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Re: Can't get Oxygen Sensor reading

Postby Steve Smith » Thu Jun 19, 2014 2:42 pm

Hi Nick, looking at the Honda waveform, depending on your location this could be a noise issue induced via the mains supply voltage. (Ground) You mentioned it is the same on multiple vehicles which suggests this could be the "set up" of the equipment.

Can you measure again with any mains disconnected from your device. (OK if this is a laptop but a bit of a problem with a desktop)

The ideal scenario to confirm that this is the influence of noisy mains would be to disconnect the mains power with the symptom evident whilst monitoring the waveform for change (Save all buffers to review before and after disconnection)

(Could you also ensure there are no battery chargers installed to the vehicle during the above test?)

I hope this helps, take care......Steve
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Re: Can't get Oxygen Sensor reading

Postby Robski » Thu Jun 19, 2014 5:15 pm

You mentioned it is the same on multiple vehicles

I missed that bit :shock:

I've never seen that much swing in a signal from mains/charger interference :?
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