DTC P1518: Starter Switch Circuit Low: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

Trouble symptom: 

Auto Start Stop does not operate.

Wiring diagram: 

• ENGINE TYPE FB

  Auto Start Stop Ref. to WIRING SYSTEM>AUTO START STOP>WIRING DIAGRAM>ENGINE TYPE FB .

  Courtesy of SUBARU OF AMERICA, INC.

• ENGINE TYPE FA

  Auto Start Stop Ref. to WIRING SYSTEM>AUTO START STOP>WIRING DIAGRAM>ENGINE TYPE FA .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DATA MONITOR  .

   Read the data of [Starter Switch] using Subaru Select Monitor. Ref. to AUTO START STOP (DIAGNOSTICS)>DATA MONITOR .

   Is [OFF] displayed in [Starter Switch]?

   Yes:  Go to  2.

   No:  The circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

   NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
2. CHECK INPUT VOLTAGE OF TCM  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the TCM connector.
   3. Start the engine.
   4. Measure the voltage between TCM connector and chassis ground.

      Connector & terminal 

      ENGINE TYPE FB

      (T21) No. 45 (+) - Chassis ground (-):

      ENGINE TYPE FA

      (B67) No. 45 (+) - Chassis ground (-):

   Is the voltage less than 1 V?

   Yes:  Check the following item and repair if necessary.

   • Model with push button start

     Repair the open circuit of harness between keyless access control module and TCM connector.

   • Model without push button start

     Open harness between ignition switch and TCM connector

     Poor contact inside the ignition switch

   No:  Check for poor contact of TCM connector. Replace the TCM if no fault is found. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580)>TRANSMISSION CONTROL MODULE (TCM) . Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION CONTROL MODULE (TCM) .