DIY Smoke Test?

Has anyone attempted a DIY smoke test on their Legacy?

 

My CEL comes on randomly and goes away at odd times (after a complete fill up, or when the tank is about to empty, sometimes when I'm on the freeway) but every time it's a P0447:

 

P0447 - Evaporative emission control system vent control low input

 

My stealership wants $90 to pull the code (I already know what it is, and they want to do it again) and $160 to do a smoke test which is bloody highway robbery. So my friend linked some Amazon smoke testers but I just saw the Youtube video where a guy made one from a pasta sauce jar, a soldering iron and a bike pump.

 

I've replaced the gas cap and also I have a charcoal box I got from a junkyard that I haven't swapped in yet... but I'm wondering how accurate a DIY smoke test would be compared to taking it into the stealership...

There may be a link to one in this thread in the past year or so.

 

https://legacygt.com/forums/showthread.php/idea-web-links-saved-various-parts-219238.html

 

Ask google too.

I bought one for around 100 bucks and called it a day, rather than try and rig something together. It works really well too, can't complain.

 

https://www.amazon.com/gp/product/B0746SL9D6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Coming on and going off on its own leads me to believe it's an intermittent issue. I'd ohm the sensor and compare it to factory specifications. Leak tests will not tell you if a solenoid or valve is bad unless you're able command it on/off or open/closed. You can pull the valve and supply your own power and ground several times to see if it opens and seals but if the resistance (ohms) are out of spec, there's no need to go further until you have a new valve.

I'm not sure I understand what you're suggesting - probably best I take it to a shop.

 

I'm more adept at mechanical work but my electrical skills need work.

Back in the old days we use to puff cigar's/hookah smoke in. Now my friend calls me to smoke the hookah for a smoke test. Since I have the lung's for it....

 

For a P0447, Vent Valve/Solenoid open circuit. You need to check the Fuel cap, hose and use a ohm meter for the sensor and solenoid like others previous mention. You can also check the wires and terminals if there corroded.

Edited May 10, 2021 by amusa

You might want to inspect the gas cap and maybe replace it. They are cheap.

He's already replaced the cap.

 

There should be a 2 pin plug on the canister from the junkyard. That is the valve in question. If you have a multimeter, set it to ohms and measure the resistance across the 2 pins. I'll see if I can find the specs for max/min allowed.

 

If you have the ability to command the valve open/closed and have a 921 or 7440 style bulb handy, bend the prongs on the bulb and insert them into the connector. While commanding the valve open or shut, the bulb should light up letting you know there is power and ground. Take it one step further and wiggle the wiring to see if the bulb cuts out indicating a broken wire.

I replaced the replacement camp (the replacement was from used loaner from a friend that doesn't have the P0447) with a new one from the stealership and the P0447 went away.

 

I now have a P0031, O2 sensor heating element low voltage