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DTC P1590: Neutral Position Switch Circuit High Input

  1. Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE  . If DTC P0705 is present, diagnose and repair DTC P0705 first. If DTC P1590 is only DTC set, go to next step.
  2. Turn ignition on. Using DVOM connected to ground, backprobe ECM connector B134 (22-pin connector) terminal No. 8. See Figure . If voltage is less than one volt with transaxle in Neutral or Park, go to next step. If voltage is not less than one volt with transaxle in Neutral or Park, go to step  5 .
  3. Turn ignition on. Using DVOM connected to ground, backprobe ECM connector B134 (22-pin connector) terminal No. 8. If voltage is 4.5-5.5 volts in all gear positions other than Neutral or Park, go to next step. If voltage is not 4.5-5.5 volts in all gear positions other than Neutral or Park, go to step  5 .
  4. Check for poor terminal contact in ECM connector. Repair as necessary. If terminal contact is okay, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
  5. Using DVOM connected to ground, backprobe ECM connector B134 (22-pin connector) terminal No. 8. If voltage is more than 10 volts, locate and repair short to voltage in wiring between ECM and inhibitor switch. If voltage is not more than 10 volts, go to next step.
  6. Turn ignition off. Disconnect ECM connector B134 (22-pin connector) and 12-pin inhibitor switch connector. Using an ohmmeter, measure resistance between ECM connector B134 (22-pin connector) terminal No. 8 and inhibitor switch connector terminal No. 12. See Fig 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 and check for poor terminal contact in connectors between inhibitor switch and ECM.
  7. Using an ohmmeter connected to ground, measure resistance at inhibitor switch connector terminal No. 7. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, locate and repair open circuit in wiring and check for poor terminal contact in connectors between inhibitor switch and starter. Also check starter circuit and starter motor.
  8. Measure resistance of inhibitor switch between terminals No. 7 and No. 12 with transaxle in Park and Neutral. If resistance is less than one ohm in both positions, go to next step. If resistance is not less than one ohm in both positions, replace inhibitor switch.
  9. Check for any problem in selector cable connection to inhibitor switch. Repair connection as needed. If no problems are located in selector cable connection to inhibitor switch, 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  .
    Fig 1: Inhibitor Switch Connector Terminal Identification
    G00013024Courtesy of SUBARU OF AMERICA, INC.
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