CHRS electric coolant pump replacement - how hard?

1. As long as the check engine light is not on, I personally would not worry about the CHRS pump. It adds almost zero value.
2. If you are determined to ignore my #1 above, then yes, replacing the pump is easy. Just raise up the left front corner of the car, support with a jack stand, remove the tire and the front part of the fender liner, and you will see the CHRS canister and the CHRS pump. You may need to remove the engine undercover on the driver's side of the vehicle for further access.
3. Disconnect the 12V battery.
4. If you want to drain and replace the engine coolant, this is the perfect opportunity. Measure the amount of drained coolant so that you know when to declare victory as you refill. If you open the CHRS canister drain (without opening the radiator cap) that will vent out around 95% of the coolant that can come out of the system, without having to also open the radiator and engine block drains. If you don't want to drain the engine coolant, just move on to #5.
5. Replace the pump. Reconnect the 12V battery.
6. Fill engine coolant. Remove the large black plastic cover over the radiator for access to the radiator cap. There are six plastic fasteners that look like, but are not, screws. Rotate the fastener with a Philips screwdriver as you exert upwards force on the cover, to pop each fastener out. If a fastener breaks (the plastic is especially brittle in cold weather) then replace at your local Toyota dealer's parts counter. You will need ~6 US quarts of Toyota Super Long Life Coolant if you had drained per #4 above. (The rated capacity is ~9 US quarts but substantial fluid is trapped in the heater core and associated plumbing.)

It is not easy to get the air out of the engine coolant system. The Lisle yellow plastic funnel designed for this purpose is extremely useful. My posts #22 and #42 here, as well as surrounding discussion, may also be helpful:
Changing engine coolant | Page 2 | PriusChat
7. Replace the fender liner and engine undercover. Replace the tire. Lower the car, tighten the wheel lug nuts to 76 ft.-lb.

 

Hi Patrick. I don't know if you still check this site but had a few questions for you. My check engine has been coming on for about a 1,000 miles now and its throwing the code for the CHRS pump, which I noticed does not work anymore. Obviously I need to replace this ASAP, hope I'm not doing any damage to the car. When I remove the pump, is coolant going to leak? if so how much? I recently had the coolant flushed, so I would like to avoid having to get another flush. Can I just top it off? Or do I need to go through the entire process of removing any trapped air?

 

You are not doing damage to the car. Yes, coolant will leak when the pump is removed. You can reduce the coolant loss by plugging the hose openings or by applying clamps to the hoses.

You can top off the coolant. If you allow substantial coolant to be lost then you will have to manually run the CHRS pump to get air out of the CHRS canister.