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DTC P0452: EVAP System Pressure Sensor Low Input

  1. Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE  . Turn ignition off. Remove and reinstall fuel filler cap. Turn ignition on. Using scan tool, observe fuel tank pressure. If pressure is less than -0.83 in. Hg, go to next step. If pressure is not less than -0.83 in. Hg, system has returned to normal. Check for intermittent open or short in wiring or poor terminal contact in connectors between fuel tank pressure sensor and ECM. See WIRING DIAGRAMS article.
  2. Using a DVOM connected to ground, backprobe ECM connector B135 (28-pin connector) terminal No. 9. See Figure . If voltage is more than 4.5 volts, go to step  4 . If voltage is not more than 4.5 volts, go to next step.
  3. Using a DVOM connected to ground, backprobe ECM connector B135 (28-pin connector) terminal No. 9 while wiggling harness and ECM connector. If voltage changes more than 4.5 volts while wiggling harness and ECM connector, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and fuel tank pressure sensor. If voltage does not change more than 4.5 volts while wiggling harness and ECM connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
  4. Using a DVOM connected to ground, backprobe ECM connector B135 (28-pin connector) terminal No. 15. If voltage is less than 0.2 volt, go to step  6 . If voltage is not less than 0.2 volt, go to next step.
  5. Using scan tool, observe fuel tank pressure while wiggling harness and ECM connector. If pressure changes more than -0.83 in. Hg while wiggling harness and ECM connector, check for poor terminal contact at ECM connector. If pressure does not change more than -0.83 in. Hg while wiggling harness and ECM connector, go to next step.
  6. Turn ignition off. Move rear seat cushion and disconnect Gray 6-pin in-line connector located between rear wiring harness and fuel tank harness. Turn ignition on. Check voltage between ground and ECM-side of Gray 6-pin in-line connector terminal No. 5. See Figure If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and Gray 6-pin in-line connector. See WIRING DIAGRAMS article.
  7. Turn ignition off. Disconnect ECM connector B135 (28-pin connector). Using an ohmmeter, measure resistance between ECM connector B135 (28-pin connector) terminal No. 19 and ECM-side of Gray 6-pin in-line connector terminal No. 1. 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 terminal contact in connectors between ECM and Gray 6-pin in-line connector. See WIRING DIAGRAMS article.
  8. Measure resistance between ground and ECM-side of Gray 6-pin in-line connector terminal No. 1. If resistance is more than 500 k/ohms, go to next step. If resistance is not more than 500 k/ohms, locate and repair short to ground in wiring between ECM and Gray 6-pin in-line connector.
  9. Disconnect fuel tank pressure sensor connector. Measure resistance between fuel tank pressure sensor harness connector terminal No. 3 and fuel-tank side of Gray 6-pin in-line connector terminal No. 5. See Figure and Fig 1 . If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open in fuel tank harness.
    Fig 1: ECM-Side Of Fuel Pump Harness Connector Terminal Identification
    G00013017Courtesy of SUBARU OF AMERICA, INC.
  10. Measure resistance between fuel tank pressure sensor harness connector terminal No. 1 and fuel-tank side of Gray 6-pin in-line connector terminal No. 1. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, locate and repair open in fuel tank harness.
  11. Measure resistance between ground and fuel tank pressure sensor harness connector terminal No. 2. If resistance is more than 500 k/ohms, go to next step. If resistance is not more than 500 k/ohms, locate and repair short to ground in fuel tank harness.
  12. Check for poor terminal contact at fuel tank pressure sensor connector. If terminal contact is okay, replace fuel tank pressure sensor. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
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