I have a 2004 Impreza TS that had the Check Engine LIght (CEL) on for a P1443 - " EVAP Control System Vent Control Function Problem ".
The fix was to replace Purge Valve control solenoid, P/N: 16102AA080 - located under the intake manifold on the passenger side of the engine. This part is the same as on a '97 Legacy that I recently had, so it's a common part that Subaru has used for years. And due to the cost, would be worth trying a used one (if you can return it). New runs $90+.
This didn't cause the car to run/drive any differently but it did have a related side-effect: When refilling the fuel tank, the car would stumble / Idle poorly / fail to start on the 1st try. This only lasted for 30 seconds and the car started and ran fine otherwise. I did NOT have the refueling issue that causes the gas nozzle to turn off prematurely, which seemed to come up more often with the P1443 code (see attached for diagnosing that issue.)
If you get the code, use the Diagnostic tests attached FIRST before spending a dime. Basically, w/the key off, connect the green connectors under the driver's side of the dash, key to ON >>>engine OFF, and ensure all the solenoids involved are clicking and airflow isn't continuous while clicking...the valve should open/close causing the airflow to be interrupted.
History (but not a recommend troubleshooting sequence!):
I spoke to a Subaru parts supplier that I've used for the last few years and he suggested, after talking to a tech, to replace the Canister Vent Valve also known as the Drain Valve, P/N: 42084FA120. This is in the back behind the passenger rear wheel underneath the car for the 1999-2004 Subaru Impreza (includes the WRX and STi) and Forester. I think it's the same for Legacy and Outback. (Based on other threads, the Canister Vent/Drain valve was integrated into the charcoal canister on '05+ models.)
This is a pic of the parts in the EVAP system. The Canister vent valve solenoid/Drain Valve (top of pic next to the cylindrical drain filter) and the pressure control solenoid on the lower right located in back of the car, the Charcoal Canister (underneath everything) and the purge valve control solenoid (the separate part w/the hose) from the intake manifold.
After this had no effect I replaced the Charcoal Canister and cleaned out the Drain Filter. This was also a no go.
For reference the charcoal canister weighs less than 3 lbs. when new but when diagnosing issues, many techs will replace it if it weighs 4-5 lbs.. Also, if you have a habit of 'topping off' - STOP IT - you're likely back feeding fuel into places it's not supposed to go - such as the charcoal canister.
Finally, I got my act together and found a document online and was given one by the Subaru parts dealer (see attached) that recommended using the green diagnostic connectors under the dash (Video HERE). This cycles all the solenoids, radiator fans, etc on/off to verify that they are @ least getting power.
Also Fairtax4me gave me the following good info:
the Drain valve (canister vent valve) is the valve referenced by this code.
The drain valve solenoid is closed by the ECU at certain times, to diagnose leaks in the evap system. It looks like its supposed to be open normally to allow fresh air to enter and exit the canister.
Use the test mode plugs to check the drain valve for operation. It should click on and off in roughly one second intervals. If it doesn't click check for battery voltage reaching the plug. Then check the other pin in the plug for continuity to ground. It should fluctuate between ground and no ground as the ECU toggles the ground side of the circuit.
If it clicks, try to blow air through the valve while in test mode to make sure the valve seals properly.
You may also have a problem with the purge control solenoid under the intake manifold sticking open <this WAS MY ISSUE!!>. If the purge solenoid sticks open it draws vacuum on the canister all the time when the engine is running. It also allows fuel vapors from refueling to enter the engine right after starting, which makes the fuel mixture too rich. It basically floods the engine, which could cause it to stall. If the engine is warm the O2 sensors pick up on this and the ECU then adjusts the fuel mixture way lean to try to compensate, which could also cause it to stall.
Blow air through the purge solenoid while in test mode to make sure it seals properly. If it doesn't seal properly you can try blowing some compressed air through the ports to dislodge any crud that may be in the valve. Some of the purge valves you can disassemble and clean the valve seat and the bore it sits in.
I checked that the two in the back - Canister vent valve solenoid/Drain Valve and Pressure Control Solenoid, and then the Purge Valve Control Solenoid @ the intake manifold. The Purge valve wasn't cycling and when I blew thru it, air was able to flow continuously....it was stuck OPEN.
I swapped in an extra Purge Valve I had and tested it. As well as cycling on/off, it also turned the air flow on/off as i blew thru it......problem found! I drove the car for 30 minutes and the CEL stayed off, whereas before it would come on w/in 5-10 minutes of cruising on the freeway AND when I put in some fuel it started and ran fine. I'm calling it FIXED....after much frustration.
Here's a pic of the Purge Valve disassembled. I can't see anything wrong w/it, but some have indicated they might be able to be fixed???:
Edited by wtdash, 04 January 2014 - 08:41 PM.