I've looked into this in the past and as I analyze the data from other cars I notice something odd about mine. I'm wondering if its model and make specific or perhaps an underlying issue. I'm always wanting to keep my Accord in good condition.

If the info I read was correct, with the introduction of downstream and upstream sensors in a car, they were made with two different types of data collection: Analog and Digital.

The upstream o2 sensor, collecting data for AFR, is said to send digital signals. The downstream, reading the cat converter efficiency, is analog.

When I analyze different cars using a scan tool I see the spikes (digital) of the upstream sensor and the flat lines (analog) of the downstream sensor. However on my car I see analog data coming from both sensors. My car is a 97 Accord. Is that how the sensors were designed or is there a problem? They are aftermarket sensors, would a downstream sensor placed in the upstream spot cause this?

I'm curious since I would think that a digital signal would provide quicker and more accurate AFR readings for the computer.

Any ideas? I would love to learn more about the nuances in o2 sensor design and behavior.

Thanks

 

The sensors are all analog, but I think you're mis-using the term.

Your sensors are narrow-band (both of em). What that means is the signal is kinda like a switch. On or off, not much in between. Still analog, but your car's system can't really operate with enough resolution to get a stable reading at some intermediate value. Just like you can't operate a normal light switch as a dimmer, just by holding the lever in the middle.

Not sure how you're getting a stable reading, unless it's running open-loop? Your EFI system is supposed to hunt back & forth with the sensor switching "ON" & "OFF" several times per second. In fact the old-school way to check for a lazy sensor is to measure it with an analog voltmeter & watch the needle swing quickly back & forth.

Starting with 2003 Accords (maybe ULEV engines in earlier years) have a wide-band sensor in the front position. That one has a proportional signal over some range of oxygen content. So maybe that's what you are calling an "analog" sensor?

 

I posted this on another forum originally and I got a response that basically explained the types of sensors that would be digital. So I see that they are analog. However I still wonder why the 98 lx i monitored showed sharper spikes.

Ill have to post a screen shot to show what I mean. I'm trying to learn how to work with different cars since I'm just used to how my car acts.

 

I forgot to mention that I was also wondering if ECUs contain digitizers or convert the analog signals to digital signals to improve response time as well.

The o2 sensors themselves wouldnt make sense to have digitizers but would it make sense for it to be converted?

 

Yeah, it makes sense that it would be digitized internally, but I didn't think that was what you were asking. Back in the early days of O2 sensors the whole system was analog, but that goes back to Bosch in the early 70s.