DTC 21 Discrepancy In Relays (On)

DTC detecting condition:

Drive does not match between brake vacuum pump relay and brake vacuum pump.

Trouble symptom:

Brake vacuum pump does not operate.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance.

Wiring diagram:

Fig 1: Brake Vacuum Pump Relay And Brake Vacuum Pump - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

Fig 2: Brake Vacuum Pump Relay And Brake Vacuum Pump - Diagnostic Procedure Chart (1 Of 2)

Courtesy of SUBARU OF AMERICA, INC.

Fig 3: Brake Vacuum Pump Relay And Brake Vacuum Pump - Diagnostic Procedure Chart (2 Of 2)

Courtesy of SUBARU OF AMERICA, INC.