Malfunction Of Lumbar Operation

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

CHECK SWITCH .
1. Turn the ignition switch to OFF.
2. Disconnect the power seat switch connector.
3. Measure the resistance between connector terminals when moving the switch to lumbar forward and lumbar backward. Ref. to SEATS>POWER SEAT>INSPECTION>POWER SEAT SWITCH
Is the inspection result normal?

Yes : Go to 2.

No : Replace the power seat switch assembly. Ref. to SEATS>POWER SEAT
CHECK HARNESS .
1. Disconnect the lumbar motor connector.
2. Measure the resistance between power seat switch connector and lumbar motor connector.
  Connector & terminal
  
  (St52) No. 18 - (St70) No. 2:
  
  (St52) No. 9 - (St68) No. 1:
Is the resistance less than 10 Ω?

Yes : Go to 3.

No : Check power seat harness.
CHECK LUMBAR MOTOR .
1. Connect the power seat switch connector and lumbar motor connector.
2. Apply battery voltage to the lumbar motor and check the motor rotation.
  Connector & terminal
  
  (St70) No. 2 (+) - (St70) No. 1 (-):
  
  (St70) No. 1 (+) - (St70) No. 2 (-):
Does the motor rotate normally?

Yes : Check for temporary poor contact or mechanical trouble (flat mat & hook spring assembly) in lumbar support mechanism.

No : Lumbar motor problem. Replace the flat mat & hook spring assembly.