P0446, Techstream TBP Fail, and CCV Replacement

I have read the other P0446 threads and seems as if most people replaced the charcoal canister and VSV (valve closest to the canister). I managed to dry fit the VSV and canister without removing the canister and it didn't work for me. I also replaced the EVAP VSV (next to the intake) and that didn't work for me.


If you review cip0441 (seen below), you will see that P0446 (only) has two causes: VSV or VSV CCV. I already tried VSV so the only thing left is the VSV CCV (vacuum switch valve for canister closed valve, or tank bypass valve). Unfortunately, the VSV CCV is on top of the gas tank. It is on the passenger side, towards the front of the car.

The VSV CCV is called the canister filter with outlet valve (77730-47030).

The Prius fuel and evap pdf shows all the EVAP components and what each of them look like. The official instructions state that you have to drop the exhaust and the entire fuel tank. Luckily, I didn't have to drop the exhaust and managed to replace it by lowering the gas tank so that it bottoms out on the exhaust.

Before you start, make sure to have two car jacks, or one car jack and the prius spare tire jack. Also, drain the tank as much as possible. I got it down to 3 bars so I had enough to run the evap test.

1. Jack up the rear of the car on both sides. You will need to use two jack stands to hold up the car since you will need the jack to support the gas tank. I don’t recommend using ramps since it will limit your maneuverability under the car.

2. Find the two straps holding up the gas tank. Support the gas tank with the two jacks right under the straps.. I used the hydraulic jack for the driver side and the mechanical prius jack for the passenger side so I had better control when I lowered the passenger side of the tank. Remove all four bolts. I used an impact wrench to remove it and it was easy to remove. Don’t lower the gas tank just yet.

3. Remove the rear seat bottom, undo the fuel pump cover, unplug the fuel pump and other electrical connectors. Move the fuel pump cover away from the hole (it won’t move that far).

4. Start lowering the tank. You will need to lower both sides of the tank since if you lower just one side, the other side is still pinned to the car. Lower both sides so that the passenger side of the tank bottoms out on the exhaust pipe.

5. Go back into the car to remove the right bolts holding the CCV valve onto the gas tank. You can reach through the gas pump opening to remove the right bolt. You will need to go under the car to remove the left CCV bolt. You will be able to see the bolt besides the CCV.

6. Disconnect the electrical connector. Also unclip the large black hose from the gas tank. You probably won’t be able to remove the connector.

7. Remove the metal plate just next to the CCV. It is held in by three small bolts. It is accessible from inside the rear seats. This will help you remove the CCV/Filter via the opening in the back seat.

8. Once the CCV is loose, remove the CCV from the gas tank. This isn’t easy since the gasket is really tight. I used a screw driver to pry part of it up. Try reaching the CCV from under the car and move the entire filter/CCV side to side to remove it. This part is easiest from under the car.

9. Once the CCV is removed, go back inside the car and ease the CCV towards the opening. Now you should have enough room to unhook the hose from the CCV.

10. Once you remove the CCV/Filter from the car, put in the new one. Plug the hose into the CCV and put it back near the gasket. Go under the car and plug into the gas tank. This is the hardest step. I palmed the CCV/Filter and pressed down on the gasket while rocking the CCV back and forth until I seated it into the gas tank. I didn’t get very far from inside the car and only did it from under the car.

11. Once CCV is installed, plug the electrical connector and screw on the two bolts. Don’t forget the ground cable. Clip the hose back onto the gas tank.

12. Reinstall the metal plate with the three bolts.

13. Start jacking up the gas tank. Once you get the straps close enough, you can start putting in the bolts. Once you have put in all four bolts, slowly tighten each bolt. Move the gas tank if necessary. You can remove both jacks once four bolts are on the car. Tighten all four bolts.

14. Hang the muffler back on the supports.

15. Go inside the car to plug in the fuel pump, all electrical connectors and put the fuel pump cover back on. Reinstall rear seat bottom.

With Techstream, clear all DTC and then re-run the EVAP test. It should pass at this point. I drove the car on three trips with only about 10 miles total and when I came back, the car had all monitors pass since I forced the EVAP test to run before I started driving.