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DTC P0108: Intake Manifold Pressure Sensor Circuit High Input

  1. Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE  . Start engine. Using scan tool, observe intake manifold absolute pressure. If pressure reads more than 38.39 in. Hg, go to step  10 . If pressure does not read more than 38.39 in. H, go to next step.
  2. Using 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. Measure voltage between ground and ECM connector B135 (28-pin connector) terminal No. 9 while wiggling wiring and ECM connector. 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 while wiggling wiring and ECM connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
  4. Using DVOM connected to ground, backprobe ECM connector B135 (28-pin connector) terminal No. 8. If voltage is less than 0.7 volt, go to step  6 . If voltage is not less than 0.7 volt, go to next step.
  5. Using scan tool, observe atmospheric absolute pressure while wiggling wiring and ECM connector. If reading changes more than 0.51 in. Hg while wiggling wiring and ECM connector, repair poor terminal contact at ECM connector. If reading does not change more than 0.51 in. Hg while wiggling wiring and ECM connector, go to next step.
  6. Turn ignition off. Disconnect intake manifold pressure sensor connector. Turn ignition on. Check voltage between ground and intake manifold pressure sensor connector terminal No. 3. 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 manifold pressure sensor. See WIRING DIAGRAMS article.
  7. Turn ignition off. Disconnect ECM connector B135 (28-pin connector). Measure resistance between ECM connector B135 (28-pin connector) terminal No. 8 and intake manifold pressure sensor 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 between ECM and intake manifold pressure sensor.
  8. Measure resistance between ECM connector B135 (28-pin connector) terminal No. 19 and intake manifold pressure sensor connector terminal No. 2. 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 manifold pressure sensor.
  9. Check intake manifold pressure sensor connector for poor terminal contact. Repair as necessary. If connector is okay, replace intake manifold pressure sensor.
  10. Turn ignition and scan tool off. Disconnect intake manifold pressure sensor connector. Turn ignition and scan tool on. Using scan tool, observe intake manifold absolute pressure. If pressure is more than 38.39 in. Hg, locate and repair short to voltage in wiring between ECM and intake manifold pressure sensor. If pressure is not more than 38.39 in. Hg, replace intake manifold pressure sensor. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
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