DTC 12: Compare Error In Other Sensor

DTC detecting condition: 

Error in comparison with other brake booster relative pressure

Trouble symptom: 

Brake vacuum pump does not operate.

Wiring diagram: 

Vacuum pump control system Ref. to WIRING SYSTEM>VACUUM PUMP CONTROL SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK BRAKE VACUUM HOSE. 
   1. Turn the ignition switch to OFF.
   2. Check the status of the brake vacuum hose connection.

   Is the brake vacuum hose connected firmly?

   Yes:  Go to  2.

   No:  Connect the brake vacuum hose.

2. CHECK BRAKE VACUUM HOSE. 
   1. Turn the ignition switch to ON and start engine.
   2. Check for leakage from the brake vacuum hose.

   Is there a leak from the brake vacuum hose?

   Yes:  Replace the brake vacuum hose.

   No:  Go to  3.

3. CHECK BRAKE BOOSTER PRESSURE SENSOR. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the brake booster pressure sensor connector.
   3. Measure the resistance between brake booster pressure sensor terminals.

   Terminals 

   No. 1 - No. 3:

   No. 2 - No. 3:

   Is the resistance 15 kΩ or less?

   Yes:  Go to  4.

   No:  Replace the brake booster. Ref. to BRAKE>BRAKE BOOSTER .

4. CHECK HARNESS BETWEEN ECM AND BRAKE BOOSTER PRESSURE SENSOR CONNECTOR. 
   1. Disconnect the connector from ECM.
   2. Measure the resistance of harness between ECM connector and brake booster pressure sensor connector terminal.

   Connector & terminal 

   (B134) No. 18 - (B565) No. 3:

   (B134) No. 19 - (B565) No. 1:

   (E158) No. 13 - (B565) No. 2:

   Is the resistance less than 1 Ω?

   Yes:  Go to  5.

   No:  Repair the open circuit of harness between ECM connector and brake booster pressure sensor connector terminal.

5. CHECK HARNESS BETWEEN ECM AND BRAKE BOOSTER PRESSURE SENSOR CONNECTOR. 

   Measure the resistance of harness between ECM connector and chassis ground.

   Connector & terminal 

   (B134) No. 18 - Chassis ground:

   (B134) No. 19 - Chassis ground:

   (E158) No. 13 - Chassis ground:

   Is the resistance 1 MΩ or more?

   Yes:  Go to  6.

   No:  Repair the short circuit to ground between the ECM connector and brake booster pressure sensor connector terminal.

6. CHECK HARNESS BETWEEN ECM AND BRAKE BOOSTER PRESSURE SENSOR CONNECTOR. 

   Measure the voltage between ECM connector and chassis ground.

   Connector & terminal 

   (B134) No. 18 (+) - Chassis ground (-):

   (B134) No. 19 (+) - Chassis ground (-):

   (E158) No. 13 (+) - Chassis ground (-):

   Is the voltage 0.5 V or less?

   Yes:  Go to  7.

   No:  Repair the short circuit to power supply in harness between the ECM connector and brake booster pressure sensor connector terminal.

7. CHECK BRAKE BOOSTER PRESSURE SENSOR POWER SUPPLY. 
   1. Connect the brake booster pressure sensor connector.
   2. Turn the ignition switch to ON.
   3. Measure the voltage between ECM connector terminals.

   Connector & terminal 

   (B134) No. 18 (+) - (B134) No. 19 (-):

   Is the voltage 4.75 - 5.25 V?

   Yes:  Go to  8.

   No:  Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (W/O STI)>ENGINE CONTROL MODULE (ECM) .

8. CHECK CURRENT DATA. 
   1. Connect the ECM connector.
   2. Turn the ignition switch to ON.
   3. Depress the brake pedal several times, until the pedal becomes firm.
   4. Read the current data of brake vacuum pump system using Subaru Select Monitor. Ref. to BRAKE VACUUM CONTROL (BVC) (DIAGNOSTICS)>SUBARU SELECT MONITOR>OPERATION>READ CURRENT DATA .

      Is the «Atmosphere Pressure»«Brake Booster Pressure»-1 -+1 kPa?

      Yes:  Temporary poor contact occurs.

      No:  Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (W/O STI)>ENGINE CONTROL MODULE (ECM) .