Generic O2 sensor vs B1S1 O2 Sensor

Hi all,

I had a question about how the scanner reads O2 sensors. I have a 2004 Chevy Monte Carlo LS with a 3.4 that I am troubleshooting an EGR issue with. It may be that I have a stray voltage somewhere, or a bad ground somewhere. The issue I am curious about however is where the Generic O2 sensor reading comes from, as it is reading differently from the B1S1 O2 sensor. This engine only has Bank 1 sensors, upstream and downstream, and what I see is the Generic sensor having a discreet line at the same voltage as the downstream O2 sensor, otherwise tracking the movement of the Upstream O2 sensor. I'll edit this post with a link to a screenshot of what i mean shortly.

Does this make sense to anyone?

TIA

Screenshot showing O2 weirdnessAttachment 129859

Screenshot showing O2 generic much narrower than O2 B1S1, and EGR Issue's I'm chasing Attachment 129860

Log files would be more helpful than screenshots. But my first thought would be that the SAE data is sometimes really useful, but almost always the manufacturer-specific PIDs will be what you want to look at. On rare occasions the OE data will use substituted values when there is a fault condition, I'm thinking specifically of ECT when there's a current P0128.

Quote:

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Originally Posted by blindsquirrel

Log files would be more helpful than screenshots. But my first thought would be that the SAE data is sometimes really useful, but almost always the manufacturer-specific PIDs will be what you want to look at. On rare occasions the OE data will use substituted values when there is a fault condition, I'm thinking specifically of ECT when there's a current P0128.

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Funny you mention that. I have NEVER been fond of Snap On scanners. I spent about 5 times more on a MasterTech from Vetronix. One of the guys at the dealership I was at was going to spend all the money on a S/O and I told him not to. He did it anyways and one of the first vehicles he used it on gave him the substitute data. He fought that thing all day. I went over asked him what was going on and told him his new scanner was a piece of sh*t. Plugged mine in and dang if it didn't say -40 on coolant temp. Bad connector. I told him to give it back but he didn't.

Oddly enough after reviewing the Log from my drive into work, the strange spikes on the generic O2 were there, until i adjusted the scale, then they disappeared. Looks like it might be an display error when watching live data, as when the bar moves on VCM scanner during review, the artifacting goes away. It's strange, maybe I should just ignore it. However, since you asked for a log file, might as well send you the last one i have. The generic O2 does still have less of a range than the B1S1, but it is at least tracking once the erroneous values go away.Attachment 129866