DTC P0890: TCM Power Relay Sense Circuit Low: Notes

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DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Improper gear shifting

Wiring diagram:

DC power supply circuit Ref. to WIRING SYSTEM>POWER SUPPLY CIRCUIT>WIRING DIAGRAM .

CVT control system Ref. to WIRING SYSTEM>CVT CONTROL SYSTEM .

Engine electrical system Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Use the check board when measuring the TCM/ECM terminal voltage and resistance.
After servicing or replacing faulty parts, perform the last step of the basic diagnostic procedure.

CHECK HARNESS.
1. Disconnect the TCM connector.
2. Remove the main relay.
3. Measure the resistance between TCM connector and M/B.
  Connector & terminal
  
  (T10) No. 8 - (M/B) No. 3:
  
  (T10) No. 24 - (M/B) No. 3:
  
  (T10) No. 40 - (M/B) No. 3:
  
  Is the resistance less than 1 Ω?
  
  Yes: Go to 2.
  
  No: Repair the open circuit of harness.
CHECK HARNESS.
1. Disconnect the ECM connector.
2. Measure the resistance between ECM connector and M/B.
  Connector & terminal
  
  (B134) No. 12 - (M/B) No. 4:
  
  Is the resistance less than 1 Ω?
  
  Yes: Go to 3.
  
  No: Repair the open circuit of harness.
CHECK HARNESS.
Measure the resistance between TCM connector and chassis ground.

Connector & terminal

(T10) No. 8 - Chassis ground:

(T10) No. 24 - Chassis ground:

(T10) No. 40 - Chassis ground:

Is the resistance 1 MΩ or more?

Yes: Go to 4.

No: Repair the short circuit of harness.
CHECK RELAY POWER SUPPLY.
Measure the voltage between M/B and chassis ground.

Connector & terminal

(M/B) No. 1 (+) - Chassis ground (-):

(M/B) No. 2 (+) - Chassis ground (-):

Is the voltage 10 V or more?

Yes: Go to 5.

No: Repair the open or short circuit of harness.
CHECK MAIN RELAY.
1. Turn the ignition switch to OFF.
2. Check the main relay. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>MAIN RELAY>INSPECTION .
  Is the check result OK?
  
  Yes: Go to 6.
  
  No: Replace the main relay.
CHECK INPUT SIGNAL FOR TCM.
1. Connect all connectors.
2. Install the main relay.
3. Read the data of [Control module voltage] using Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR .
  Is [Control module voltage] 10 V or more?
  
  Yes: Current condition is normal. Check for poor contact in connectors or harnesses, and repair the defective part.
  
  No: Go to 7.
CHECK MAIN RELAY.
1. Turn the ignition switch to OFF.
2. Replace the main relay.
3. Using the Subaru Select Monitor, perform the clear memory. Ref. to COMMON (DIAG)>CLEAR MEMORY .
4. Read the DTC using Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC P0890 displayed?

Yes: Replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580)>TRANSMISSION CONTROL MODULE (TCM) .

No: The original main relay is defective.