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DTC P0453 (TNKP_Hi): EVAP Emission Control System Pressure Sensor High Input (All Except Legacy)

  1. Turn ignition off. Remove and reinstall fuel filler cap. Connect scan tool. Turn ignition on. Observe fuel tank pressure sensor signal. If displayed value is 0.827 in. Hg or less, go to next step. If displayed value is more than 0.827 in. Hg, go to step 8) for Forester and 2.5L Impreza or go to step 7) for 2.2L Impreza.
  2. Using voltmeter connected to ground, backprobe PCM connector terminal No. 21 (Red wire) with ignition on. If voltage reading is more than 4.5 volts, go to next step. If voltage reading is 4.5 volts or less, wiggle PCM connector. If voltage reading changes to 4.5 volts or more, check for an open in harness between PCM and fuel tank pressure sensor. If okay, check for poor contact to PCM. If voltage reading does not change, replace PCM.
  3. Using voltmeter connected to ground, backprobe PCM connector terminal No. 4 (Green/Orange wire). If voltage reading is less than 0.2 volt, go to next step. If voltage reading is more than 0.2 volt, observe fuel tank pressure sensor signal. Check if value changes to more than -0.827 in. Hg when wiggling PCM connector. If value changes, repair wiring or poor contact at PCM connector. If value does not change when wiggling PCM connector, go to next step.
  4. Turn ignition off. Remove right rear quarter interior trim panel. Disconnect fuel tank pressure sensor connector. Turn ignition on. Check voltage between ground and fuel tank pressure sensor connector terminal No. 3 (Red wire). If voltage reading is more than 4.5 volts, go to next step. If voltage reading is 4.5 volts or less, check for an open in harness between PCM and fuel tank pressure sensor connector.
  5. Turn ignition off. Disconnect PCM connector. Using an ohmmeter, check resistance of harness between PCM connector terminal No. 4 and fuel tank pressure sensor connector terminal No. 1 (Green/Orange wire). If resistance is one ohm or less, go to next step. If resistance is more than one ohm, check for an open in harness between PCM and fuel tank pressure sensor connector.
  6. Check resistance of harness between fuel tank pressure sensor connector terminal No. 2 and PCM connector terminal No. 20 (Red/Green wire). If resistance is one ohm or less, check for poor contact at fuel tank pressure sensor connector. If connection is okay, replace fuel tank pressure sensor. If resistance is more than one ohm, check for an open in harness between PCM and fuel tank pressure sensor connector.
  7. Turn ignition off. Remove fuel tank. Remove fuel tank cord from fuel tank. Connect fuel tank cord to rear wiring harness. Remove and reinstall fuel filler cap. Turn ignition on. Observe fuel tank pressure sensor signal. If displayed value is 0.827 in. Hg or less, replace fuel tank pressure sensor. If displayed value is more than 0.827 in. Hg, repair short in harness between PCM and fuel tank pressure sensor.
  8. Turn ignition off. Remove right rear quarter interior trim panel. Disconnect fuel tank pressure sensor connector. Remove and reinstall fuel filler cap. Turn ignition on. Observe fuel tank pressure sensor signal. If displayed value is 0.827 in. Hg or less, replace fuel tank pressure sensor. If value is more than 0.827 in. Hg, check for short in harness between PCM and fuel tank pressure sensor.
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