DTC P0816: Downshift Switch Circuit

DTC detecting condition: When malfunctioning mode continues for 60 s or more

Trouble symptom: Manual gear shifting not possible

CAUTION:

Before performing diagnosis, record the freeze frame data.
After servicing or replacing faulty parts, perform the last step of the basic diagnostic procedure. Ref. to TRANSMISSION (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .

Wiring diagram: AT control system Ref. to WIRING SYSTEM>AT CONTROL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CHECK INPUT SIGNAL FOR TCM (CHECK RECURRENCE OF MALFUNCTION) .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor, read data of [Down Switch] in [Data Monitor] of [Transmission], while not operating the paddle shift switch and the select lever switch. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR .
Is "OFF" displayed in [Down Switch]?

Yes: Go to 2.

No: Go to 3.
CHECK INPUT SIGNAL FOR TCM (OPERATION CONFIRMATION) .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor, read data of [Down Switch] in [Data Monitor] of [Transmission], while operating ON/OFF for the paddle shift switch and the select lever switch. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR .
Does the [Down Switch] display change between "ON" and "OFF" according to the operation?

Yes: Go to 8.

No: Go to 3.
CHECK PADDLE SHIFT SWITCH DOWN SIDE (DIAGNOSIS FOR SWITCH UNIT STUCK ON, SHORT CIRCUIT) .
1. Turn the ignition switch to OFF.
2. Disconnect the paddle shift switch connector.
3. Measure the resistance between paddle shift switch connector terminals.
  Connector & terminal
  
  (Sg22) No. 1 - (Sg22) No. 4:
Is the resistance 1 MΩ or more?

Yes: Go to 4.

No: Replace the paddle shift switch. Ref. to POWER ASSISTED SYSTEM (POWER STEERING)>STEERING SWITCH .
CHECK PADDLE SHIFT SWITCH DOWN SIDE (DIAGNOSIS FOR SWITCH UNIT STUCK OFF, POOR CONTINUITY) .
1. Turn the ignition switch to OFF.
2. Measure the resistance between paddle shift switch connector terminals.
  Connector & terminal
  
  (Sg22) No. 1 - (Sg22) No. 4:
Is the resistance less than 1 Ω?

Yes: Go to 5.

No: Replace the paddle shift switch. Ref. to POWER ASSISTED SYSTEM (POWER STEERING)>STEERING SWITCH .
CHECK SELECT LEVER SWITCH DOWN SIDE (DIAGNOSIS FOR PADDLE SHIFT SWITCH STUCK ON, SHORT CIRCUIT) .
1. Turn the ignition switch to OFF.
2. Disconnect the select lever switch connector.
3. Measure the resistance between the select lever switch connector terminals.
  Connector & terminal
  
  (i145) No. 12 - (i145) No. 13:
Is the resistance 1 MΩ or more?

Yes: Go to 6.

No: Replace the select lever assembly. Ref. to CONTROL SYSTEMS>SELECT LEVER .
CHECK SELECT LEVER SWITCH DOWN SIDE (DIAGNOSIS FOR PADDLE SHIFT SWITCH STUCK OFF, POOR CONTINUITY) .
1. Turn the ignition switch to OFF.
2. Measure the resistance between the select lever switch connector terminals.
  Connector & terminal
  
  (i145) No. 12 - (i145) No. 13:
Is the resistance less than 1 Ω?

Yes: Go to 7.

No: Replace the select lever assembly. Ref. to CONTROL SYSTEMS>SELECT LEVER .
CHECK HARNESS (DIAGNOSIS FOR SHORT CIRCUIT TO GROUND BETWEEN TCM AND SWITCH CIRCUIT) .
1. Turn the ignition switch to OFF.
2. Disconnect the TCM connector.
3. Measure the resistance between TCM connector and chassis ground.
  Connector & terminal
  
  (B81) No. 14 - Chassis ground:
  
  (B81) No. 20 - Chassis ground:
Is the resistance 1 MΩ or more?

Yes: Go to 8.

No: Repair the short circuit of harness.
CHECK FOR POOR CONTACT .
Check poor contact of the paddle shift switch circuit.

Is the check result OK?

Yes: Replace the TCM. Ref. to AUTOMATIC TRANSMISSION>TRANSMISSION CONTROL MODULE (TCM) .

No: Repair the poor contact.