DTC P0890: TCM Power Relay Sense Circuit Low: Notes

DTC detecting condition: 

Immediately at fault recognition

Trouble symptom: 

Improper gear shifting

Wiring diagram: 

Power supply circuit Ref. to WIRING SYSTEM>Power Supply Circuit>WIRING DIAGRAM

Engine electrical system Ref. to WIRING SYSTEM>Engine Electrical System>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK ECM CONNECTOR. 

   Check the connecting condition of ECM connector.

   Is the ECM connector correctly connected?

   Yes:  Go to  2

   No:  Connect the ECM connector correctly.

2. CHECK HARNESS BETWEEN M/B FUSE AND MAIN RELAY CONNECTOR. 
   1. Turn the ignition switch to OFF.
   2. Measure the voltage between M/B fuse and engine ground.

      Connector & terminal 

      (M/B fuse) No. 26 (+) - Engine ground (-):

   Is the voltage 10 V or more?

   Yes:  Repair the harness and connector.

   NOTE: In this case, repair the following item:
   • Short circuit to power supply of harness between M/B fuse and main relay connector
   • Defective main relay

   No:  Go to  3

3. CHECK HARNESS BETWEEN ECM AND MAIN RELAY CONNECTOR. 
   1. Turn the ignition switch to OFF.
   2. Remove the main relay.
   3. Disconnect the ECM connector.
   4. Measure the resistance between the ECM connector and engine ground.

      Connector & terminal 

      (B134) No. 60 - Engine ground:

   Is the resistance 1 MΩ or more?

   Yes:  Repair the poor contact of ECM connector.

   No:  Repair the short circuit to ground in harness between ECM connector and main relay connector.