P0446 diagnostics

  • 2 POSTS
  • 1.8L
  • 4 CYL
  • FWD
  • 150,000 MILES

Hello everyone,

I failed a smog check due to P0446 code. I took out EVAP purge valve from under the hood, applied nine volts to it, it clicked. I assumed it works. Then I hoisted the car up to access EVAP vent valve and the canister. I unplugged as many hoses as I could (not all) but enough to access vent solenoid (valve). After applying twelve volts to it, it clicked, so I assumed it is working. I visually inspected hoses and pipes underneath and it looked good. The canister did not look cracked to leaking. I got frustrated since both solenoids in system appeared to be in working condition.

I read TSB here - https://www.2carpros.com/questions/toyota-corolla-1998-toyota-corolla--5

I could not measure the voltage between terminals in ECM, because I believe the ECM is fine, but I measured voltage on EVAP purge solenoid connection wires. With ignition 'on' it read 0.18 volts. Is not too low?
I also measured voltage on air filter wires and it was five volts. Way more than on purge valve.

So my first question is, is measuring voltage on wires is different than measuring voltage on ECM terminals? My guess it is a different thing, but then, why is the voltage on purge valve wires so low?

Thank you!

Do you
have the same problem?
Thursday, June 8th, 2017 AT 6:26 PM

1 Reply

  • 14,304 POSTS


Reading voltage at any point in the system is the same. Here is an engine wiring diagram (below) so you can test the wiring of the EVAP system. Also check the gas cap O ring to make sure it is not leaking. If there are any leaks in the system it will give you this code as well.

Please run some tests and get back to us so we can continue helping you.

Cheers, Ken

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Monday, June 12th, 2017 AT 1:52 PM

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