DTC C1921: Parking Position Switch Circuit

DTC detecting condition:

A fault is detected if the switch was positioned at lock or release continuously for 90 seconds while the vehicle is stopped.
A fault is detected if an irregular switch condition continues for a predetermined period of time immediately after the switch position is changed. A fault is also detected if the switch condition is not confirmed afterwards.
A fault is detected if the switch harness is open or shorted.

Trouble symptom:

Parking brake system does not operate.

DTC detecting condition:

Parking brake/brake fluid level warning light system Ref. to WIRING SYSTEM>PARKING BRAKE/BRAKE FLUID LEVEL WARNING LIGHT SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CHECK OPERATION OF ELECTRONIC PARKING BRAKE.
Operate the parking brake switch.

Does the electronic parking brake operate properly?

Yes : Ask the customer whether the following switch operation was performed.
- Operated slowly over one second or more.
- Repeated ON/OFF operation several times within one second. When the case above is true, the system is normal.
  When it is normal, a temporary poor contact or noise interference is a possible cause.
No : Go to 2.
CHECK HARNESS (CHECK FOR OPEN CIRCUIT).
1. Turn the ignition switch to OFF.
2. Disconnect the connectors from the VDCCM & H/U and parking brake switch.
3. Measure the resistance between VDCCM & H/U and parking brake switch connector.
  Connector and terminal
  
  (B310) No. 17 - (i163) No. 2:
  
  (B310) No. 18 - (i163) No. 5:
  
  (B310) No. 19 - (i163) No. 1:
  
  (B310) No. 20 - (i163) No. 4:
Is the resistance less than 1 Ω?

Yes : Go to 3.

No : Repair harness and connector between VDCCM & H/U and parking brake switch connector.
CHECK HARNESS (CHECK FOR GROUND SHORT CIRCUIT).
Measure the resistance between the parking brake switch connector and chassis ground.

Connector and terminal

(i163) No. 2 - Chassis ground:

(i163) No. 5 - Chassis ground:

(i163) No. 1 - Chassis ground:

(i163) No. 4 - Chassis ground:

Is the resistance 1 MΩ or more?

Yes : Go to 4.

No : Repair ground short of harness between VDCCM & H/U and parking brake switch connector.
CHECK HARNESS (CHECK FOR SHORT CIRCUIT TO POWER SUPPLY).
1. Turn the ignition switch to ON.
2. Measure the voltage between parking brake switch connector and chassis ground.
  Connector and terminal
  
  (i163) No. 2 (+) - Chassis ground (-):
  
  (i163) No. 5 (+) - Chassis ground (-):
  
  (i163) No. 1 (+) - Chassis ground (-):
  
  (i163) No. 4 (+) - Chassis ground (-):
Is the voltage less than 1 V?

Yes : Go to 5.

No : Repair short to power supply of harness between VDCCM & H/U and parking brake switch connector.
CHECK PARKING BRAKE SWITCH.
Check the parking brake switch. Ref. to PARKING BRAKE>PARKING BRAKE SWITCH>INSPECTION .

Is the check result OK?

Yes : Go to 6.

No : Replace the parking brake switch. Ref. to PARKING BRAKE>PARKING BRAKE SWITCH .
CHECK VDCCM & H/U.
1. Connect all connectors.
2. Using the Subaru Select Monitor, perform the clear memory. Ref. to COMMON (DIAG)>CLEAR MEMORY .
3. Execute the inspection mode. Ref. to BRAKE CONTROL (DIAGNOSTICS)>INSPECTION MODE .
4. Read the DTC using Subaru Select Monitor. Ref. to BRAKE CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is the same DTC displayed?

Yes : Replace the VDCCM & H/U. Ref. to VEHICLE DYNAMICS CONTROL (VDC)>VDC CONTROL MODULE AND HYDRAULIC CONTROL UNIT (VDCCM & H/U) .

No : Go to 7.
CHECK DETECTION OF OTHER DTCS FOR VDC.
Read the DTC using Subaru Select Monitor. Ref. to BRAKE CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

Is any other DTC displayed?

Yes : Perform the diagnosis according to DTC. Ref. to BRAKE CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .

No : Currently, it is normal. There may have been a temporary poor contact in the harness and connector or a temporary noise interference.