O2 Sensor issues

[stutaeng]

My 99 Burb is a 5.7, but here's my experience with the O2 sensors. I've had this truck 8 years, most of its use in the last 4 years. I've replaced the downstream ones twice in that 4 years, when I had codes indicating they were bad. Replaced the front one on driver side ( bank 1) last year because it was coding bad. Original unit to best of my knowledge.
Now I'm getting codes for bad O2 sensors, bank 1,sensor 1. Which would be the one that's the newest one on the truck. I would have thought that if one was bad, it'd be the passenger side upstream one, since it's original. Only one that hasn't been replaced. My inspection guy hasn't been able to get a good reading on his scanner yet; it keeps saying that the systems are" not ready to scan", hence no data available to give more indication of the exact problem.
Any hints? I'd like to get this Burb inspected and registered, so I don't have to watch out for picky police! Thanks in advance!

"not ready to scan?" I've never heard of that one...You just select the O2 live stream graph and looks for a positive and negative (between -1.0V and positive 1.0V) oscillating waveform. Just make sure your engine is in closed loop.

If the O2 is faulty you will not see this. Either the graph is pegged and no response if you flip the gas pedal.

 

[kennythewelder]

My 99 Burb is a 5.7, but here's my experience with the O2 sensors. I've had this truck 8 years, most of its use in the last 4 years. I've replaced the downstream ones twice in that 4 years, when I had codes indicating they were bad. Replaced the front one on driver side ( bank 1) last year because it was coding bad. Original unit to best of my knowledge.
Now I'm getting codes for bad O2 sensors, bank 1,sensor 1. Which would be the one that's the newest one on the truck. I would have thought that if one was bad, it'd be the passenger side upstream one, since it's original. Only one that hasn't been replaced. My inspection guy hasn't been able to get a good reading on his scanner yet; it keeps saying that the systems are" not ready to scan", hence no data available to give more indication of the exact problem.
Any hints? I'd like to get this Burb inspected and registered, so I don't have to watch out for picky police! Thanks in advance!

I was told years ago, that it is best to change all 02 sensors at the same time, because the ECM compares data between them, but I know this is true between the rear and front sensors. I have had a CEL in my wifes 4 runner (a 02 sensor code) for several years. Those sensors are very expensive, so I called my local Toyota dealer. They claim that they only change whats bad. I tried that with no luck on the 4 Runner. I tried everything I know to do, but still can get the code to go away, and stay away. I even took it to a custom exhaust shop, and had them check it for leaks. There are none. The sensors for our trucks are not that expensive, so you may want to replace the 2 front sensors, and see if that works. Other option is to do a libe data read where you can see whats going on. Are the voltage spikes the same? Is the wave pattern the same on both banks? By the way, people have been asking about the car show at Blackem. IDK, havent heard anything. There are 4 shows in town this Sat and 2 on Sunday. We will see if the rain holds off. If so, they should be sone good shows. One is at the Harley shop on I-10. Sat morning 9 to 3 PM.

 

[Supercharged111]

"not ready to scan?" I've never heard of that one...You just select the O2 live stream graph and looks for a positive and negative (between -1.0V and positive 1.0V) oscillating waveform. Just make sure your engine is in closed loop.

If the O2 is faulty you will not see this. Either the graph is pegged and no response if you flip the gas pedal.

Not -1V to +1V, 0-1V with decimals out to the thousandths.

 

[stutaeng]

Not -1V to +1V, 0-1V with decimals out to the thousandths.

Oops! Yes: 0.000 to 1.000

 

[Schurkey]

And if you don't have a "waveform" to look at, the scan tool should give you "Crosscounts" or something similar.

That'd be the number of times the sensor flips from rich to lean, or lean to rich. Higher number is better. 10-ish is acceptable, I'd rather see 20-ish. My truck goes to 0 crosscounts at idle, I'm told that replacing the non-heated O2 sensor with a heated sensor will fix that.

 

[HotWheelsBurban]

I was told years ago, that it is best to change all 02 sensors at the same time, because the ECM compares data between them, but I know this is true between the rear and front sensors. I have had a CEL in my wifes 4 runner (a 03 sensor code) for several years. Those sensors are very expensive, so I called my local Toyota dealer. They claim that they only change whats bad. I tried that with no luck on the 4 Runner. I tried everything I know to do, but still can get the code to go away, and stay away. I even took it to a custom exhaust shop, and had them check it for leaks. There are none. The sensors for our trucks are not that expensive, so you may want to replace the 2 front sensors, and see if that works. Other option is to do a libe data read where you can see whats going on. Are the voltage spikes the same? Is the wave pattern the same on both banks? By the way, people have been asking about the car show at Blackem. IDK, havent heard anything. There are 4 shows in town this Sat and 2 on Sunday. We will see if the rain holds off. If so, they should be sone good shows. One is at the Harley shop on I-10. Sat morning 9 to 3 PM.

I have the monthly hot wheels show Saturday. I haven't heard anything more about the Bayou Roundup either. The Lone Star Roundup in Austin has been moved to Labor Day weekend ( again this year) so we'll see if it goes well and if they do another show in LA. That show has had a small but loyal audience, but I'm not sure if the guys are going to do 2 shows in as many months. We shall see though. I want to come back to Lafayette and eat good food and see cool people!

 

[Pinger]

That'd be the number of times the sensor flips from rich to lean, or lean to rich. Higher number is better. 10-ish is acceptable, I'd rather see 20-ish. My truck goes to 0 crosscounts at idle,I'm told that replacing the non-heated O2 sensor with a heated sensor will fix that.

That is probably correct.
I fitted an AFR gauge on the dash last year and it showed pretty tardy activity - but slightly better at higher loads/speeds.
At the weekend found that my heated O2 sensors were lacking the current to their heating elements. With that reinstated the AFR gauge is pretty frisky leaping from each end of the scale with alacrity.

(Full scale in my case but that is on LPG and the system is underdamped. The new found responsiveness of the AFR gauge (due to improved O2 sensor response - they are also what the LPG system is responding to) means I can close down the extremes of swing and narrow it closer to stoich at all times).

 

[PlayingWithTBI]

That is probably correct.
I fitted an AFR gauge on the dash last year and it showed pretty tardy activity - but slightly better at higher loads/speeds.
At the weekend found that my heated O2 sensors were lacking the current to their heating elements. With that reinstated the AFR gauge is pretty frisky leaping from each end of the scale with alacrity.

Just an FYI. Here's an example of the difference between a NBO2 and a WBO2. The NBO2 (orange line) doesn't really tell you what the AFR is, it just pretty much switches between high and low mVs. The WBO2 (purple line) is more accurate. So, according to the NBO2 it looks like it's running fine while the WBO2 shows it's just a little on the lean side.

Anyway, this is an example of what "cross counts" (180 in this case) means - number of times switching above and below 450mV in a period of time which IIRC is 1 minute.

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[Pinger]

Just an FYI. Here's an example of the difference between a NBO2 and a WBO2. The NBO2 (orange line) doesn't really tell you what the AFR is, it just pretty much switches between high and low mVs. The WBO2 (purple line) is more accurate. So, according to the NBO2 it looks like it's running fine while the WBO2 shows it's just a little on the lean side.

In fairness to the narrow band sensor, if you take the average (over the 7 steps) to find the median it too shows lean - just not as obviously as the wide band displays it. The WB output is significantly more easily read though.

 

[PlayingWithTBI]

The WB output is significantly more easily read though.

And it'll read from 7.35 - 22 AFR where the NBO2 can't so, you can tune better for HLC and WOT too.