Well doing the injector balance test is how gm service info says to check those, they used to have the old-style injector tester. The fuel pressure spec is 60 to 66 PSI, so if it's staying there at 62 that's okay, but it shouldn't be going back into open loop. In open loop it only calculating its fuel strategy from the coolant temperature sensor, map, MAF etc, and ignores the 02 sensors until their voltages are swinging enough, so the ECM might not be seeing a good signal form them, or it might need a hard reset. Below is the description on Run modes. If the RPM is too high, it might go back to open loop. But it sounds like you may want to reset the ECM and check the 02 sensors in Global obd2 data and see if there's a difference. Having to keep your foot on the gas to keep it running tells me there is not enough air flow, or the pulse width on the injectors is too low. Have you pulled any plugs to see what they look like? Go back to the basics on this one. You might have the correct fuel pressure but not enough volume, dirty MAF, EGR stuck slightly open, those are things I would check. Since its a 5.7l the MAF should be around 5.8g/s at idle, I would graph all 3 oxygen sensors and see if the front 2 are swing and the rear one is steady. If all 3 mirror each other that points to a bad Cat.
These are all the things I look for in live data, and Im not sure what Autel you have, but they do pretty good with the amount of live data PIDS they provide. There's something there that will be out of place,
But the open loop is the clue, its reverting back to it because it's not seeing a good signal from an oxygen sensor, or the sensor is too slow. When they get lazy and frequency is low, it will go back to open loop as well. It does sound like the Fuel tank pressure is high, so it's possible the vent valve is stuck closed or something, but that wouldn't put it back into open loop. It would just fail the Evap readiness monitors and set a code.
Can you get a pulse width on the injectors for this vehicle, I know you said your fuel trims are good, but with no codes, that data might not be correct. But go back over data again, If the vehicle has secondary air injection, that's something that will cause a false 02 reading as well.
Sorry for long post, I added some more run mode info below that might help.
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Tuesday, February 7th, 2023 AT 11:29 AM