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DTC P0453 (TNKP_HI): EVAP EMISSION CONTROL SYSTEM PRESSURE SENSOR HIGH INPUT (LEGACY) Subaru Forester SF

Testing & Diagnostics ~566 words
  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 9).
  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 (Yellow/Blue wire). If voltage reading is 0.2 volt or less, go to next step. If voltage reading is more than 0.2 volt, observe fuel tank pressure sensor signal on scan tool. 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 rear seat cushion. Separate rear wiring harness and fuel tank cord. Turn ignition on. Using voltmeter connected to ground, measure voltage at rear wiring harness connector terminal No. 1 (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 rear wiring harness connector.
  5. Turn ignition off. Disconnect PCM connector. Using an ohmmeter, check resistance of harness between PCM connector terminal No. 4 and rear wiring harness connector terminal No. 4 (Yellow/Blue 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 rear wiring harness connector.
  6. Measure resistance of harness between ground and rear wiring harness connector terminal No. 2 (Red/Black wire). If resistance is one ohm or less, go to next step. If resistance is more than one ohm, check for short to ground in harness between PCM and rear wiring harness connector.
  7. Remove fuel tank. Disconnect fuel tank pressure sensor connector. Measure resistance of fuel tank cord (Yellow/Blue wire) between terminals of opposing ends of harness. If resistance is more than one ohm, repair open in fuel tank cord. If resistance is one ohm or less, go to next step.
  8. Measure resistance of fuel tank cord (Red/Black wire) between terminals of opposing ends of harness. If resistance is more than one ohm, repair open in fuel tank cord. If resistance is one ohm or less, check fuel tank pressure sensor connector for poor contact. Repair as necessary. If connection is okay, replace fuel tank pressure sensor.
  9. 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.

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