Hi,
EGR stands for exhaust gas recirculation. the EGR valve allows a specific amount of exhaust to re-enter the engine combustion chamber via the intake. The ultimate goal is to reducing NOx gasses from entering the atmosphere.
Based on your description, start by checking for engine vacuum leaks. This can cause the vehicle to idle poorly and shifting issues.
Here is a link that shows how to check for leaks:
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
Also, you may want to consider having the can-bus system scanned. CAN stands for controller area network. This network connects all the modules/computers together via a few wires. By scanning the can-bus, it will identify codes from any of the modules.
Here is a video showing how it's done:
https://youtu.be/InIlnsjOVFA
In all honesty, that is where I would start.
Let me know what you find or if you have other questions.
Take care,
Joe
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Friday, March 26th, 2021 AT 8:01 PM