Hello, what codes are the PCM setting? If it doesn't pass the IM Readiness monitors for the Oxygen sensors after 2 drive cycles, it will set codes. So, there must be something stored in the PCM. If the oxygen sensor switching time or the sensors are hanging high or low voltage, it won't pass any monitors, Ill post the list of codes, but also checking the exhaust back pressure to determine any Catalytic Converter failures would be good to know as well.
But any codes we'll need to know first. That will give some direction for diagnosing the issue.
If you have a scan tool, and can check the live engine data, you can take a look at the Oxygen sensors voltage levels and see if anything looks off. If any of the oxygen sensor heater circuits are not working, it will prevent the sensors from functioning correctly. I'm not sure what kind of shop you've had it at, but they should have given you a more in-depth answer about what exactly is wrong with the PCM. Such as if the memory circuit is losing or has no power. There is a battery feed that keeps power to the PCM to retain memory, which might be something they were meaning, but they should be more specific with the issue so you can get things fixed up right, instead of just replacing a computer.
But here's the service info on the IM Readiness monitors you need. So, if the PCM is not storing any codes, which almost sounds like what is happening, you can check that the PCM's memory circuit is okay.
Here are the fuses that are permanent battery feeds that retain the memory, Fuse 29 15amp, Fuse 20 15amp, and Fuse 5 7.5amp. They are kind of difficult to see on the wiring diagram. The 6th diagram shows the PCM Grounds, if there are any broken grounding straps or corroded grounds to the frame or body, or any voltage drop from the engine block to battery negative, or the frame to the battery, this can have the same effect as a bad PCM ground. So, check those fuses for power on both sides, here are some guides to help.
We should be able to help you figure out why you're not getting the monitors passed.
https://www.2carpros.com/articles/how-to-check-a-car-fuse
https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester
https://www.2carpros.com/articles/how-to-use-a-voltmeter
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Monday, July 3rd, 2023 AT 4:15 PM