DTC P0453: EVAP System Pressure Sensor High Input - Legacy & Outback 2.5L

Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . Turn ignition off. Remove and reinstall fuel filler cap. Using scan tool, observe fuel tank pressure. If pressure is more than 0.83 in. Hg, go to step 12. If pressure is not more than 0.83 in. Hg, go to next step.
Using a DVOM connected to ground, backprobe ECM connector B136 (30-pin connector) terminal No. 15. 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.
Using DVOM connected to ground, backprobe ECM connector B136 (30-pin connector) terminal No. 15 while wiggling harness and ECM connector. If voltage changes more than 4.5 volts while wiggling harness and ECM connector, locate and repair poor terminal contact in ECM connector. If voltage does not change more than 4.5 volts while wiggling harness and ECM connector, replace ECM.
Using DVOM connected to ground, backprobe ECM connector B136 (30-pin connector) terminal No. 12. 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.
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, locate and repair poor terminal contact in ECM connector. If pressure does not change more than -0.83 in. Hg while wiggling harness and ECM connector, go to next step.
Turn ignition off. Disconnect 6-pin in-line connector located between rear harness and fuel tank harness (under rear seat), nearest fuel tank. Turn ignition on. Measure voltage between ground and ECM-side of 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 6-pin in-line connector. See WIRING DIAGRAMS article.
Turn ignition off. Disconnect ECM connector B136 (30-pin connector). Using an ohmmeter, measure resistance between ECM connector B136 (30-pin connector) terminal No. 12 and ECM-side of 6-pin in-line connector terminal No. 6. 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 6-pin in-line connector.
Measure resistance between ECM connector B136 (30-pin connector) terminal No. 16 and ECM-side of 6-pin in-line connector terminal No. 3. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, located and repair short to ground in wiring between ECM and 6-pin in-line connector.
Disconnect fuel tank pressure sensor connector. Measure resistance between fuel tank pressure sensor harness connector terminal No. 2 and fuel-pump side of 6-pin in-line connector terminal No. 6. See Figure and 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 fuel tank harness.
Measure resistance between fuel tank pressure sensor connector terminal No. 1 and fuel-pump side of 6-pin in-line connector terminal No. 3. 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 fuel tank harness.
Check for poor terminal contact at fuel tank pressure sensor connector. Repair connector as required. If terminal contact is okay, replace fuel tank pressure sensor.
Turn ignition off. Disconnect fuel tank pressure sensor connector. Turn ignition on. Using scan tool, observe fuel tank pressure. If pressure is more than .83 in. Hg, locate and repair short to power in wiring between ECM and fuel tank pressure sensor. If value is not more than .83 in. Hg, replace fuel tank pressure sensor. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES and VERIFICATION PROCEDURE .