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Follow up on prior question 7/22 re PO446EVP sys. vent control charcoal canister

(1998 Toyota Camry)
in Fort Lauderdale, FL on September 08, 2011
Ck Engine light lit again now (6 wks later)Took to dealer-they put on their diag computer (even though I showed them the results of the one from Tires Plus- Dealer says its the evp sys vent charcoal canister-Cost to replace: $619.53-says the valves themselves are ok-but the charcoal canister just needs replacing. Says if I "top off" when filling up with gas, it causes overflow into the canister and ruins it. Does any of this seem reasonable to you experts? I bought the car new and have never had this prob before-p.s.133K gentle miles.The dealer didn't reset the ck engine light so its still on. Now if anything else goes wrong,I won't know cause the light is already on. Help!
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Popular Answer
of Greg Solow's Engine Room on September 08, 2011
We see lots of problems with the canisters and valves,Toyota used to sell the valves mounted on the canister separately but replacing the canister and valves complete assembly cures the problem if the codes stored pertain to the canister and valves. The hose up at the air filter gets knocked off during air filter replacement but I am sure that got checked, the two electric solenoid valves in the engine compartment also fail intermittently but again I am sure that was checked. Canister replacement is quite simple Under the car at rear above rear sub frame.
on September 09, 2011
Replace Vent valve
Repair open, short, or resistance problem in control circuit
Repair open, or short, or resistance problem in power circuit
Replace PCM
on September 08, 2011
The car is 13 years old, the canister is plastic.There's some info.

Vehicle Application: 1998 Toyota Camry 2.2L, Vin G, Eng Cfg L4, Eng Des 5SFE

Customer Concern: Check engine light is on with a code P0446. On the early evaporative systems, this code is for a leak in the charcoal canister.
Tests/Procedures: 1. Verify that the 3-way Vacuum Switching Valve (VSV) on the canister operates correctly. When the VSV is not grounded, the Fuel Tank Pressure (FTP) sensor should be connected to the canister side of the system only. When the VSV is grounded, then the FTP sensor should monitor only the fuel tank.

2. Monitor the FTP sensor, unplug the 3-way VSV, draw a vacuum into the canister and verify that it will hold vacuum and the pressure sensor voltage will decrease.

3. Test and verify that the purge solenoid and wire harness are all OK. The purge solenoid should apply vacuum to the charcoal canister when grounded. Also verify that the hose from the purge solenoid to the charcoal canister does not leak.

4. On a 1998 Camry, we have seen a few problems with the connector under the backseat cushion. The connector has the wires for the pressure sensor and the VSV under the vehicle.
Potential Causes: Charcoal Canister
Leaking Evaporative Hose

Tech Tips: It is common for the 3-way VSV to stick or not operate correctly or for the charcoal canister to be faulty. The charcoal canister has many check valves and springs built inside, so always replace the canister and 3-way VSV as an assembly so the code does not reset.
Diagnostic Codes: P0446
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