lost mt STFT??? HELP!
#11
TECH Resident
Not sure there is anything wrong with any of the O2 sensors. The only strange outputs from the scanner are that the STFTs that are identified on both of the downstream sensors are not showing any data (in %'s). One shows n/a% and the other is totally blank. The "live" graphics on both are a blank screen. All other "monitor" stuff shows a live graphic.
Were you getting any codes since you mentioned emmision tests?
#12
Now I get it. I just assumed there should be sensor 2 STFT data since they have a data entry point - then "n/a%" makes sense!
No codes - the only indicators are that the evap and O2 sensors are not ready. These two have been consistent for hundreds of miles and a number of drive cycles. I'm using "Car Scanner" on my iphone, but have not purchased the "pro" package. Wondering if the upgrade will allow me to do the bidirectional testing you've suggested. Is there something fairly obvious to look for about the O2 sensors on the data dumps?
No codes - the only indicators are that the evap and O2 sensors are not ready. These two have been consistent for hundreds of miles and a number of drive cycles. I'm using "Car Scanner" on my iphone, but have not purchased the "pro" package. Wondering if the upgrade will allow me to do the bidirectional testing you've suggested. Is there something fairly obvious to look for about the O2 sensors on the data dumps?
#13
TECH Resident
Now I get it. I just assumed there should be sensor 2 STFT data since they have a data entry point - then "n/a%" makes sense!
No codes - the only indicators are that the evap and O2 sensors are not ready. These two have been consistent for hundreds of miles and a number of drive cycles. I'm using "Car Scanner" on my iphone, but have not purchased the "pro" package. Wondering if the upgrade will allow me to do the bidirectional testing you've suggested. Is there something fairly obvious to look for about the O2 sensors on the data dumps?
No codes - the only indicators are that the evap and O2 sensors are not ready. These two have been consistent for hundreds of miles and a number of drive cycles. I'm using "Car Scanner" on my iphone, but have not purchased the "pro" package. Wondering if the upgrade will allow me to do the bidirectional testing you've suggested. Is there something fairly obvious to look for about the O2 sensors on the data dumps?
As far as the O2, look at the waveform. It should oscillate from about 0.1V to 0.90V in a sine form. If you are not getting codes, then they are most likely okay.
Check out one of these videos from these guys on EVAP systems for GM vehicles:
#14
I disconnected and cleaned the O2 sensor cables - upon reconnect and scanning, I lost both S1 signals and check engine light came on with low voltages and lean run codes. After disconnecting, pushing harder on all wires, it appears all the connections are now working and the O2 sensors are doing the wave thing. I cleared codes, so now I have a bunch not readies back again. I'm thinking now's the time to disconnect the battery and start fresh - which has seemed to work to ready the O2 sensors in many cases.
I'll get back after I'm able to "drive cycle" tomorrow!
I'll get back after I'm able to "drive cycle" tomorrow!
The following users liked this post:
strutaeng (05-24-2023)
#15
TECH Resident
I disconnected and cleaned the O2 sensor cables - upon reconnect and scanning, I lost both S1 signals and check engine light came on with low voltages and lean run codes. After disconnecting, pushing harder on all wires, it appears all the connections are now working and the O2 sensors are doing the wave thing. I cleared codes, so now I have a bunch not readies back again. I'm thinking now's the time to disconnect the battery and start fresh - which has seemed to work to ready the O2 sensors in many cases.
I'll get back after I'm able to "drive cycle" tomorrow!
I'll get back after I'm able to "drive cycle" tomorrow!
The drive cycle for every ECU check should only be like 30-40 miles in my experience.
#16
I've cleared codes, disconnected the battery, reconnected and did a drive cycle. No DTCs, but now 3 not readies - cat htr, evap and O2 sensor. Going to do a cold start tomorrow morning to see if the cat htr sets. Going for a 100 mile trip this weekend - we'll see if the others ready up - or at least the O2 sensor so I can get it passed. If there's any specific readouts I should look for, let me know.
Thanks for all your help.
Thanks for all your help.
#17
After several drive cycles this morning, only the evap and O2 sensor are not ready. At least I'm back to where I started! I'll be driving quite a bit over the holiday weekend, so if there's anything I should be monitoring with my app, let me know.
#18
Some new data when engine warmed up and kept between 2000 and 2500 rpm for over 5 minutes:
I'll recheck after my 100 mile trip this weekend.
Any tips appreciated (no $$s required)
- both upstream O2 sensors oscillate rapidly between 0.1 and 0.8 volts
- both downstream O2 sensors stay quite steady at .74 volts
- both banks STFTs range at -0.6 to +1.5 %
- both banks LTFTs stay at -0.7%
I'll recheck after my 100 mile trip this weekend.
Any tips appreciated (no $$s required)
The following users liked this post:
strutaeng (05-26-2023)
#19
TECH Resident
Some new data when engine warmed up and kept between 2000 and 2500 rpm for over 5 minutes:
I'll recheck after my 100 mile trip this weekend.
Any tips appreciated (no $$s required)
- both upstream O2 sensors oscillate rapidly between 0.1 and 0.8 volts
- both downstream O2 sensors stay quite steady at .74 volts
- both banks STFTs range at -0.6 to +1.5 %
- both banks LTFTs stay at -0.7%
I'll recheck after my 100 mile trip this weekend.
Any tips appreciated (no $$s required)
Where are you finding that these are a rich condition? 🤔
You are supposed to add up the LTFT and STFT and they ideally sum to 0, or as close to 0. You are very close to 0. I don't see anything wrong with your data.
The ECU has capability to continuously monitor and make instaneous fine adjustments based on fuel trims. Around+/- 15% is when it triggers the "money light." On my trucks when I check if they are around less than 3-5% I call it good.
Last edited by strutaeng; 05-26-2023 at 02:08 PM.
#20
This is the article:
https://www.vehicleservicepros.com/s...sfire-concerns
It's possible I've miss-interpreted, but this was the statement:
"This happens so consistently that you can look at the datastream during the misfire event and if STFT has changed less than 15 percent positive and the downstream oxygen sensor has voltage higher than 650mV that you can with confidence look for an ignition related concern to be the cause of the misfire."
Even if this single "test" that I did indicates a rich condition, I'm certainly not sure it has anything to do with the O2 sensor not readying. Simply a confusing data point?
https://www.vehicleservicepros.com/s...sfire-concerns
It's possible I've miss-interpreted, but this was the statement:
"This happens so consistently that you can look at the datastream during the misfire event and if STFT has changed less than 15 percent positive and the downstream oxygen sensor has voltage higher than 650mV that you can with confidence look for an ignition related concern to be the cause of the misfire."
Even if this single "test" that I did indicates a rich condition, I'm certainly not sure it has anything to do with the O2 sensor not readying. Simply a confusing data point?