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Ask Dan Your Own Question
Dan, Technician
Category: Subaru
Satisfied Customers: 23746
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Have trouble code p0448. trying to figure out why, yes.

Customer Question

have trouble code p0448. trying to figure out why
JA: Tell me a bit more about what's going on so he can help you best. Are you hoping to fix this yourself?
Customer: yes. retired mechanic. 2005 forester x
JA: Great! What have you tried so far?
Customer: no issues other then light on and code 448. i have power to it. connected green connector under dash. vent valve makes no noise, no click, nothing
JA: My old Jeep sounds like a steam radiator sometimes. It must be old age. The Subaru Mechanic will know what your noise means and what to do about it. Is there anything else the Subaru Mechanic should be aware of about your Subaru?
Customer: nothing more then what i just wrote
JA: Our top Subaru Mechanic is ready to take your case. Just pay the $5 fully refundable deposit and I'll fill the Subaru Mechanic in on everything we've discussed. You can go back and forth with the Subaru Mechanic until you're 100% satisfied. We guarantee it.
Submitted: 1 year ago.
Category: Subaru
Customer: replied 1 year ago.
i thought someone was waiting for me
Expert:  Dan replied 1 year ago.

Hello, my name is***** code usually means vent solenoid has failed or PCM has failed. Test the resistance of the canister vent solenoid, 25 -30 ohms, if good then use a vacuum pump to see if solenoid holds vacuum and releases it, if not then replace the solenoid. One pin on solenoid should have power with key on then other pin is grounded by PCM. If you ground pin 13 at the PCM this should ground other wire going to solenoid, if not you know it is a wiring problem. If so then you know the PCM has failed. Let me know if you have more questions or if there is anything else I can do to help. Thanks.


Customer: replied 1 year ago.
i tested the resistance. i don't have the 25-30 ohms but how do you test with vacuum pump. there is no vacuum nipple on it. just the electrical plug. thank you
Expert:  Dan replied 1 year ago.

There should be a place a vacuum line connects to it, can you send me a picture? Thanks.

Customer: replied 1 year ago.
hi dan. there was on the purge valve which is how i also tested that and found that bad. this is the vent valve that slides into the front of the vapor canister and only has the electrical plug on it. i tested it with 2 voltmeters and it's not even reading 3 ohms. here is the picture of it.
Expert:  Dan replied 1 year ago.

I see, you will need to rig something up to cover the part that slides into the canister then put vacuum into that part to see if it holds and releases. Considering resistance is out of spec I would test wire between PCM and solenoid, if good then jsut replace the solenoid/valve. Let me know how it goes, thanks.

Customer: replied 1 year ago.
thank you for the help dan. its been a while since ive gone this deep in a diagnosis. need to unplug connector at ecm first correct and then check for continuity?
Expert:  Dan replied 1 year ago.

That is correct, if you ground pin 13 at PCM this should provide the solenoid ground letting you know wiring is good. Let me know, thanks.