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DTC P0107 (P_Slow): Pressure Sensor Circuit Low Input

  1. Connect scan tool. Start engine. Observe display for intake manifold absolute pressure. If display reads less no vacuum, go to next step. If vacuum is present, system is normal. Check for poor connections or intermittent open circuits.
  2. Using voltmeter connected to ground, backprobe PCM connector terminal No. 21 (Red wire). If voltage is more than 4.5 volts, go to next step. If voltage is 4.5 volts or less, check while wiggling wiring and connector of PCM. If voltage changes, repair poor contact in wiring or PCM connector. If voltage remains more than 4.5 volts, replace PCM.
  3. Check voltage at PCM connector terminal No. 26 (Green/Orange wire on Forester and Impreza, or Green wire on Legacy). If voltage reading is less than .2 volt, go to next step. If voltage reading is .2 volt or more, observe atmospheric absolute pressure signal while wiggling PCM connector. If value changes, repair poor connection at PCM. If reading does not change, go to next step.
  4. Turn ignition off. Disconnect pressure sensor connector. Turn ignition on. Using a voltmeter connected to ground, check voltage at pressure sensor connector terminal No. 3 (Red wire). If voltage is more than 4.5 volts, go to next step. If voltage is 4.5 volts or less, check for poor contact at PCM and pressure sensor connectors. If connections are okay, check for an open circuit between PCM and pressure sensor.
  5. Turn ignition off. Disconnect PCM connector. Using an ohmmeter, check resistance of harness between PCM connector terminal No. 20 and pressure sensor connector terminal No. 1 (Red/Green wire on Forester and Impreza, or Red/Yellow wire on Legacy). If resistance is one ohm or less, go to next step. If resistance is more than one ohm, repair open in wiring between PCM and pressure sensor connectors.
  6. Check resistance of harness between ground and pressure sensor connector terminal No. 2 (Green/Orange wire on Forester and Impreza, or Green wire on Legacy). If resistance is more than 500 ohms, go to next step. If resistance is 500 ohms or less, repair short circuit in wiring between PCM and pressure sensor connector.
  7. Check pressure sensor connector for poor contact, and repair as necessary. If connection is okay, replace pressure sensor.
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