Diagnostic Procedure

1. Turn ignition switch to OFF.
2. Disconnect harness connectors from TCM and ECM.
3. Measure resistance of harness between TCM and ECM connector.

Connector & Terminal 

(B55) No. 20 - (B136) No. 11: 

Fig 1: Measuring Resistance Of Harness Between TCM & ECM Connector

CHECK: Is the resistance less than 1 ohm? 

1. YES:  Go to step 812. 
2. NO:  Repair open circuit in harness between TCM and ECM connector.

Measure resistance of harness between TCM connector and chassis ground.

Connector & Terminal 

(B55) No. 20 - Chassis ground: 

Fig 2: Measuring Resistance Of Harness Between TCM Connector & Chassis Ground

CHECK: Is the resistance more than 1 Mohm? 

1. YES:  Go to step 813. 
2. NO:  Repair short circuit in harness between TCM and ECM connector.

CHECK: Do you have a Subaru Select Monitor? 

1. YES:  Go to step  8I5.
2. NO:  Go to step 8I4. 

1. Re-connect harness connectors to TCM and ECM.
2. Start the engine, and warm-up the transmission until ATF temperature is above 80°C (176°F).
   NOTE: If ambient temperature is below 0°C (32°F) drive the vehicle until the ATF reaches operating temperature.
3. Engine idling.
4. Measure voltage between TCM connector terminals.

Connector & Terminal 

(B55) No. 20 (+) - No. 19 (-): 

Fig 3: Measuring Voltage Between TCM Connector Terminals

CHECK: Is the voltage between 1.2 and 1.8V? 

1. YES:  Even if "AT OIL TEMP" lights up, the circuit has returned to a normal condition at this time. A temporary poor contact of the connector or harness may be the cause. Repair harness or connector in the TCM and ECM.
2. NO:  Go to step  816.

1. Turn ignition switch to OFF.
2. Connect Subaru Select Monitor to data link connector.
   Fig 4: Identifying Location Data Link Connector (DLC)

   
3. Start the engine, and turn Subaru Select monitor switch to ON.
4. Warm-up the engine until engine coolant temperature is above 80°C (176°F).
5. Engine idling.
6. Read data of intake manifold pressure signal using Subaru Select Monitor.
7. Display shows intake manifold pressure signal sent from ECM.

   Is the value between 1.2 and 1.8 V? 

8. Even if "AT OIL TEMP" lights up, the circuit has returned to a normal condition at this time. A temporary poor contact of the connector or harness may be the cause. Repair harness or connector/terminals at TCM and ECM.
9. Go to step 8I6. 
   1. 8I6: CHECK POOR CONTACT. 

      CHECK: Is there poor contact in intake manifold pressure signal circuit? 

      1. YES:  Repair poor contact.
      2. NO:  Replace TCM, see TRANSMISSION CONTROL MODULE (TCM) .