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DTC P0108: Pressure Sensor Circuit High Input

  1. Perform test procedure. See TESTING PROCEDURE . Start engine. Using a scan tool, monitor intake manifold absolute pressure sensor signal. At idle, intake manifold absolute pressure sensor signal value should be more than 35.29 in. Hg. If pressure value is more than 35.29 in. Hg, go to step  10. If pressure value is not more than 35.29 in. Hg, go to next step.
  2. Using a DVOM, measure voltage by backprobing between 30-pin ECM electrical harness connector B136 terminal No. 15 (Red wire on Forester; Light Blue wire on Impreza and Outback Sport; Red/Black wire on Legacy and Outback) and good chassis ground point. 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, measure voltage by backprobing between 30-pin ECM electrical harness connector B136 terminal No. 15 (Red wire on Forester; Light Blue wire on Impreza and Outback Sport; Red/Black wire on Legacy and Outback) and good chassis ground point while wiggling ECM harness and connector. See Figure. If voltage changes more than 4.5 volts, repair poor terminal contact in ECM connector. If voltage does not change more than 4.5 volts, 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  .
  4. Using a DVOM, measure voltage by backprobing between 30-pin ECM electrical harness connector B136 terminal No. 5 (Pink/Blue wire on Forester, Impreza and Outback Sport; White wire on Legacy and Outback) and good chassis ground point. See Figure. If voltage is less than 0.2 volt, go to step  7. If voltage is not less than 0.2 volt, go to next step.
  5. Using a scan tool, monitor atmospheric absolute pressure sensor signal while wiggling ECM connector. If value does not change more than 3.94 in. Hg, go to next step. If value changes more than 3.94 in. Hg, repair poor contact in ECM connector. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
  6. Turn ignition off. Disconnect 4-pin electrical harness connector from intake air temperature and pressure sensor. Turn ignition on. Using a DVOM, measure voltage between intake air temperature and pressure sensor 4-pin electrical harness connector terminal No. 3 (Red wire on Forester, Legacy and Outback; Brown wire on Impreza and Outback Sport) and good engine ground point. 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 between ECM and intake air temperature and pressure sensor. 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  .
  7. Turn ignition off. With intake air temperature and pressure sensor 4-pin electrical harness connector disconnected, disconnect 30-pin ECM electrical harness connector B136. Using a DVOM, measure resistance between 30-pin ECM electrical harness connector B136 terminal No. 5 (Pink/Blue wire on Forester, Impreza and Outback Sport; White wire on Legacy and Outback) and intake air temperature and pressure sensor 4-pin electrical harness connector terminal No. 4 (Yellow/Black wire on Forester; Red wire on Impreza and Outback Sport; Yellow wire on Legacy and Outback). 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 wiring between ECM and intake air temperature and pressure sensor. 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  .
  8. Using a DVOM, measure resistance between 30-pin ECM electrical harness connector B136 terminal No. 16 (Red/Green wire) and intake air temperature and pressure sensor 4-pin electrical harness connector terminal No. 1 (Green/Yellow wire on Forester; Blue wire on Impreza and Outback Sport; Black wire on Legacy and Outback). 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 wiring between ECM and intake air temperature and pressure sensor. 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  .
  9. Check intake air temperature and pressure sensor electrical harness connector for poor terminal contact. Repair as necessary. If connector is okay, replace intake air temperature and pressure sensor. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
  10. Using a scan tool, monitor intake manifold absolute pressure sensor signal. If intake manifold absolute pressure sensor signal value is not more than 35.29 in. Hg, replace intake air temperature and pressure sensor. If intake manifold absolute pressure sensor signal value is more than 35.29 in. Hg, repair short to battery voltage in harness between ECM and intake manifold absolute pressure sensor. 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  .
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