EGR Cleaning: What did I get myself into?

Yes and yes. The traction battery is most important and easier to disconnect

Pixel XL ?

 

Nope to both.

 

Nope and nope.

 

I've done the whole EGR system twice, swapping in new/clean EGR Cooler + valve & cleaning the EGR pipe & intake manifold each time.
I do not disconnect the 12V batt. or disable the traction battery.

The second swap out came after ~10K. The ICE started setting an engine lean code & running as if it was lean. Eventually I found the EGR valve stuck open about 1/16". After swapping in the now cleaned original valve & cooler the Prius is back to perfect at 236K.

An interesting observation: 10K miles on my ~220K engine resulted in the EGR cooler being >50% plugged. I'm using a quart of oil every 3-4K. For me, the purpose of installing an OCC was to stop a substantial amount of oil from reaching the combustion chamber. In my case the OCC(s) are trapping <5% of the oil the ICE consumes I also find that my best OCC is the intake manifold. I have an OCC installed & after that I have an inline air line filter installed. Both collect small amounts of oil, but the real efficient OCC is the intake manifold!

 

Now just the easy part, hehe...

Take the intake airbox off too, I think? And again, I'd recommend to drain 2 liters of coolant at the radiator spigot, then the EGR cooler removal can be spill-free, as long as you lift it out carefully.

Are you going to pull the intake manifold off too? In for a penny, in for a pound? FWIW I didn't replace any gaskets, and it worked out. Only 70K kms in my case though.

 

No magnetic spark plug wrench in your tool chest?

 

Sounds like you might be in for a belated birthday present .

It is a handy tool .