DTC P0890: TCM Power Relay Sense Circuit Low: Notes

DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Improper gear shifting

CAUTION:

Use CHECK BOARD when measuring the ECM terminal voltage and resistance.
After servicing or replacing faulty parts, perform the last step of the basic diagnostic procedure. Ref. to TRANSMISSION (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .

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>WIRING DIAGRAM .

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

Courtesy of SUBARU OF AMERICA, INC.

CHECK HARNESS .
1. Disconnect the TCM connector.
2. Remove the main relay.
3. Measure the resistance between TCM connector and M/B.
  Connector & terminal
  
  (B54) No. 8 - (M/B) No. 3:
  
  (B54) No. 24 - (M/B) No. 3:
  
  (B54) 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. 49 - (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

(B54) No. 8 - Chassis ground:

(B54) No. 24 - Chassis ground:

(B54) 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) (H4DOTC)>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. Using the Subaru Select Monitor, read data of [Control module voltage] in the [Data Monitor] of [Transmission]. 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 of [Transmission]. Ref. to COMMON (diag)>CLEAR MEMORY .
  Clear Memory
4. Read the DTC of [Transmission] using the Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>Diagnostic Trouble Code (DTC) .
  Is DTC P0890 displayed?
  
  Yes : Replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION CONTROL MODULE (TCM) .
  
  No : The original main relay is defective.