DTC 21: Discrepancy In Relays(On): Wiring Diagram

Fig 1: Vacuum Pump And Main Relay - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

SYMPTOM REFERENCE

Step	Check	Yes	No
1 CHECK CONNECTOR. Check that status of the brake vacuum sensor and brake vacuum pump connection.	Are the brake vacuum sensor and brake vacuum pump connected firmly?	Go to step 2.	Connect the connector.
2 CHECK FUSE. Turn the ignition switch to OFF. Remove the brake vacuum pump fuse. Check the condition of fuse.	Is the fuse blown out?	Replace the fuse.	Go to step 3.
3 CHECK BRAKE VACUUM PUMP RELAY. Turn the ignition switch to OFF. Remove the brake vacuum pump relay from the relay box. Connect the battery to terminals No. 1 and No. 3 of the brake vacuum pump relay. Measure the resistance between the brake vacuum pump relay terminals. Terminals No. 4 - No. 5:	Is the resistance less than 1 Ω?	Go to step 4.	Replace the brake vacuum pump relay.
4 CHECK BRAKE VACUUM PUMP RELAY POWER SUPPLY. Turn the ignition switch to ON. Measure the voltage between brake vacuum pump relay connector and chassis ground. Connector & terminal (VC2) No. 1 (+) - Chassis ground (-): (VC2) No. 4 (+) - Chassis ground (-):	Is the voltage 10 V or more?	Go to step 5.	Repair the open or ground short circuit of power supply circuit.
5 CHECK HARNESS BETWEEN ECM AND BRAKE VACUUM PUMP RELAY CONNECTOR. Turn the ignition switch to OFF. Disconnect the connector of ECM. Measure the resistance of the harness between ECM and the brake vacuum pump relay connector. Connector & terminal (B136) No. 8 - (VC2) No. 3:	Is the resistance less than 1 Ω?	Go to step 6.	Repair the open circuit of harness between ECM and the brake vacuum pump relay connector.
6 CHECK HARNESS BETWEEN THE BRAKE VACUUM PUMP AND BRAKE VACUUM PUMP RELAY CONNECTOR. Turn the ignition switch to OFF. Disconnect the brake vacuum pump connector. Measure the resistance of the harness between the brake vacuum pump and brake vacuum pump relay connector. Connector & terminal (VC2) No. 5 - (B417) No. 2:	Is the resistance less than 1 Ω?	Go to step 7.	Repair the open circuit of the harness between the brake vacuum pump and the brake vacuum pump relay connector.
7 CHECK THE HARNESS BETWEEN ECM AND BRAKE VACUUM PUMP CONNECTOR. Measure the resistance of the harness between brake vacuum pump connector and the chassis ground. Connector & terminal (B417) No. 2 - Chassis ground:	Is the resistance 1 MΩ or more?	Go to step 8.	Repair the ground short of the harness between ECM and brake vacuum pump connector.
8 CHECK THE HARNESS BETWEEN ECM AND BRAKE VACUUM PUMP CONNECTOR. Measure the voltage between brake vacuum pump connector and the chassis ground. Connector & terminal (B417) No. 2 (+) - Chassis ground (-):	Is the voltage 0.5 V or less?	Go to step 9.	Repair the battery short of the harness between the ECM and the brake vacuum pump connector.
9 CHECK BRAKE VACUUM PUMP. Turn the ignition switch to OFF. Remove the brake vacuum pump. <Ref. to REMOVAL , Removal, Vacuum Pump .> Connect the battery positive terminal to the brake vacuum pump terminal No. 2, and the negative terminal to terminal No. 1.	Is the brake vacuum pump operating?	Go to step 10.	Replace the brake vacuum pump. <Ref. to BRAKE VACUUM PUMP , Vacuum Pump .>
10 CHECK BRAKE VACUUM PUMP. Connect the brake vacuum pump relay. Connect the connectors to the brake vacuum pump and ECM. Turn the ignition switch to ON. Execute the brake negative pressure pump system function check mode using the Subaru Select Monitor. <Ref. to SUBARU SELECT MONITOR . >	Is the brake vacuum pump operating?	Temporary poor contact occurs.	Replace the ECM. <Ref. to ENGINE CONTROL MODULE (ECM) . >