Operation CHARM: Car repair manuals for everyone.

P0556

DTC P0556: Brake Booster Pressure Sensor Circuit Range/Performance Problem

Special Tools Required
Vacuum pump/gauge, 0-30 in.Hg, Snap-on YA4000A or equivalent, commercially available

NOTE: If DTC P0556 is stored at the same time as DTC P0571, troubleshoot DTC P0571 first, then recheck for DTC P0556.

1. Turn the ignition switch OFF.
2. Disconnect the vacuum hose (A) for the brake booster pressure sensor (B) from the brake booster, and connect a vacuum pump/gauge, 0-30 in.Hg, to the brake booster pressure sensor hose.





3. Turn the ignition switch ON (II).
4. Check the BRAKE BOOSTER PRESSURE SENSOR in the DATA LIST with the HDS before and after applying vacuum to the hose using the vacuum pump/gauge.

Does the indicated value change?

YES - Go to step 5.

NO - Replace the brake booster pressure sensor.

5. Turn the ignition switch OFF.
6. Check for vacuum leaks or clogging at these parts:

- Brake booster pressure sensor hose.
- Brake booster vacuum hoses and their joints.
- Check valve (intake manifold).
- Check valve (vacuum pump) and filter.
- Brake booster.

Are the parts OK?

YES - Go to step 7.

NO - Repair or replace the leaking or clogged part(s).

7. Check the brake pedal position switch signal circuit.

Is the circuit OK?

YES - Go to step 8.

NO - Troubleshoot the brake pedal position switch signal circuit.

8. Reconnect the vacuum hose on the brake booster pressure sensor to the brake booster.
9. Turn the ignition switch ON (II).
10. Note the BRAKE BOOSTER PRESSURE in the DATA LIST with the HDS.
11. Turn the ignition switch OFF.
12. Make sure you have anti-theft codes for the audio and the navigation system (if equipped). Disconnect the negative cable from the battery, and wait several seconds.
13. Reconnect the negative cable to the battery, then do this procedure after the troubleshooting:

- Enter the anti-theft code for the audio system and the navigation system (if equipped).
- Set the clock.

14. Check the BRAKE BOOSTER PRESSURE SENSOR in the DATA LIST with the HDS when the electric vacuum pump runs while you turn the ignition switch ON (II). Do not start the engine.

Does the indicated value change when the motor runs?

YES - Intermittent failure, the system is OK at this time. Check for loose terminals between the electric vacuum pump relay 2 4P connector, the electric vacuum pump 2P connector, the brake pedal position switch 4P connector, and PCM. connector A (44P). Refer to intermittent failures troubleshooting. General Troubleshooting Information

NO - If the pump does not run, go to step 15. If the pump runs, turn the ignition switch OFF, then repeat steps 12 to 14 again. If you still get the same brake booster pressure sensor value, replace the electric vacuum pump.

15. Turn the ignition switch OFF.
16. Check the connection and pin fit of the electric vacuum pump 2P connector.

Is the connector properly connected?

YES - Go to step 17.

NO - Connect the electric vacuum pump 2P connector properly. If necessary, repair or replace the connector.

17. Remove electric vacuum pump relay 2, and check it.

Is the relay OK?

YES - Go to step 18.

NO - Replace electric vacuum pump relay 2.

18. Remove the No. 17 (15 A) fuse from the under-hood fuse/relay box.
19. Remove the No. 31 (7.5 A) fuse from the auxiliary under-hood fuse/relay box.
20. Check for continuity between electric vacuum pump relay 2 terminal No. 2 and No. 31 (7.5 A) fuse in the auxiliary under-hood fuse/relay box terminal No. 1.





Is there continuity?

YES - Go to step 21.

NO - Repair open in the wire between electric vacuum pump relay 2 and the No. 31 (7.5 A) fuse in the auxiliary under-hood fuse/relay box.

21. Remove electric vacuum pump relay 1.
22. Install the No. 17 (15 A) fuse in the under-hood fuse/relay box.
23. Connect electric vacuum pump relay 2 connector terminals No. 1 and No. 2, and electric vacuum pump relay 1 connector terminals No. 1 and No. 2 with jumper wires.





Does the electric vacuum pump motor run?

YES - Check for loose terminals in the electric vacuum pump relay 2 4P connector, the electric vacuum pump 2P connector, the brake pedal position switch 4P connector, and PCM connector A (44P), then update the PCM if it does not have the latest software, or substitute a known-good PCM, then go to step 1 and recheck. If no DTCs are indicated, and the PCM was substituted, replace the original PCM.

NO - Go to step 24.

24. Disconnect the electric vacuum pump 2P connector.
25. Measure voltage between body ground and electric vacuum pump 2P connector terminal No. 1.





Is there battery voltage?

YES - Go to step 26.

NO - Repair open in the wire between electric vacuum pump relay 2 and the electric vacuum pump.

26. Check for continuity between body ground and electric vacuum pump 2P connector terminal No. 2.





Is there continuity?

YES - Replace the electric vacuum pump.

NO - Repair open in the wire between the electric vacuum pump and body ground (G503).