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DTC P0447: EVAP System Vent Control Circuit Low Input

  1. Perform test procedure. See TESTING PROCEDURE . Turn ignition on. Using a DVOM, measure voltage of Brown/Yellow wire by backprobing between 35-pin ECM electrical harness connector B134 terminal No. 10 and good chassis ground point. See Figure. If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, go to step  3.
  2. Check for poor contact in 35-pin ECM electrical harness connector B134. Repair connector as required. If connector is okay, circuit has returned to normal. Check for intermittent conditions. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
  3. Turn ignition off. Disconnect 35-pin ECM electrical harness connector B134 and 2-pin drain valve electrical harness connector. See Figure, Figure and Figure . Using a DVOM, measure resistance of Brown/Yellow wire between 2-pin drain valve electrical harness connector terminal No. 2 and good chassis ground point. If resistance is not less than 10 ohms, go to next step. If resistance is less than 10 ohms, locate and repair short to ground in wiring between ECM and drain valve. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
  4. Using a DVOM, measure resistance of Brown/Yellow wire between 35-pin ECM electrical harness connector B134 terminal No. 10 and 2-pin drain valve electrical harness connector terminal No. 2. See Figure. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open circuit in wiring and check for poor contact in all connectors between ECM and drain valve. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
  5. With 2-pin drain valve electrical harness connector disconnected, use a DVOM to measure resistance across terminals of drain valve. If resistance is between 10 and 100 ohms, go to next step. If resistance is not between 10 and 100 ohms, replace drain valve. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
  6. Turn ignition on. Using a DVOM, measure voltage between 2-pin drain valve electrical harness connector terminal No. 1 (Yellow/Green wire on Forester, Impreza and Outback Sport; Yellow/Red wire on Legacy and Outback) and good chassis ground point. If voltage is more than 10 volts, go to next step. If voltage is not more than 10 volts, locate and repair open circuit and check for poor contact in all connectors between main relay and drain valve. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
  7. Check for poor contact in drain valve electrical harness connector. Repair connector as required. If connector is okay, contact authorized Subaru dealership because probable cause is deterioration of multiple parts. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
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