2003 Nissan Sentra with 199,507 miles 5 speed manual
I don’t think the upstream sensor is supposed to be stuck like that and I have to get the car inspected In July and I need some help to fix this problem. Codes are P0031, P0037
After cleaning the grounds.
and... how does it run now?
Perfect. It was the ground on the back of the intake sneaky Nissan engineers. I also cleaned the one on the cylinder head near the alternator.
I'm not sure what the "update rate" on the Bluedriver scanner is, It may be possible that you're seeing an average of what the upstream O2 sensor is reporting. The average should be around .45 volts and that screenshot doesn't show you far off at .35 volts.
What's more interesting is that both the upstream and downstream O2 sensors are reporting low voltages through those 2 trouble codes and both sensors share a common ground.
Yet you aren't complaining about any driveabilty issues.
Possibly an intermittent ground break/fault which is enough to throw the codes but not frequent enough to cause driveability issues?
No drivability issues
That upstream O2 sensor looks almost perfect after you cleaned the grounds.
Its voltage is cycling (almost evenly) above and then below the "stoichiometric switch point" of 0.45 volts.
The goal is for the computer to maintain the 14.7:1 air/fuel ratio by adjusting the length of the fuel injector pulses using the voltage readings from the upstream O2 sensor and we can see by your 2nd screenshot waveform it's doing just that, making small fuel adjustments to maintain a midpoint of 0.46 volts.
(We can't see your Fuel Trims on that screenshot so we don't know exactly how much fuel the computer is adding/subtracting to maintain control of that 14.7:1 ratio, but the point is, it's able to it)
Assuming when you cleaned up the grounds and cleared the P0031 & P0037 codes they didn't return, your IAT and ECT temps look within a reasonable value, maybe take a look at your MAF sensor's g/s reading at idle and your fuel trims and if they look good, I say you can hang up your overalls and celebrate a repair well done.
Yep
Something is not right. Follow the troubleshooting on these pages:
https://www.obd-codes.com/p0031
https://www.obd-codes.com/p0037
Yes and that sudden dip in B1S1 looks strange too. By the way, which app is that?
https://www.youtube.com/watch?v=M55qmlHZmko
BlueDriver