Code No. P0557: Brake Booster Pressure Sensor Circuit Low Input




OPERATION




FUNCTION




TROUBLE JUDGMENT


Check Conditions
Judgement Criterion

FAIL-SAFE AND BACKUP FUNCTION




PROBABLE CAUSES




DIAGNOSIS PROCEDURE


STEP 1. M.U.T.-III data list



  • Refer to Data List Reference Table .

  1. Item 171: Brake booster pressure sensor

Q. Is the check result normal?

Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Go to Step 2.

STEP 2. Perform voltage measurement at brake booster pressure sensor connector.



  • Disconnect connector, and measure at harness side.
  • Ignition switch: ON
  • Voltage between terminal BPS5 and body earth.
OK: 4.9 - 5.1 V

Q. Is the check result normal?

Go to Step 5.
Go to Step 3.

STEP 3. Check harness between brake booster pressure sensor connector terminal and engine-ECU connector terminal BPS5.



  • Check power supply line for open/short circuit.

Q. Is the check result normal?

Go to Step 4.
Repair or replace the connector, or repair the damaged harness wire.

STEP 4. M.U.T.-III data list



  • Refer to Data List Reference Table .

  1. Item 171: Brake booster pressure sensor

Q. Is the check result normal?

Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).
Replace the engine-ECU.

STEP 5. Check harness between brake booster pressure sensor connector terminal and engine-ECU connector terminal BPS5.



  • Check power supply line for damage.

Q. Is the check result normal?

Go to Step 6.
Repair or replace the connector, or repair the damaged harness wire.

STEP 6. Perform voltage measurement at brake booster pressure sensor connector.



  • Use special tool test harness (MB991658) to connect connector, and measure at pick-up harness.
  • Start up the engine and let it idle for several minutes.
  • Stop the engine, and turn the ignition switch to the ON position.
  • Depress the brake pedal several times.
  • Voltage between terminal engine-ECU BBPS line and body earth.
OK: Voltage is proportional to the brake pedal depression.

Q. Is the check result normal?

Go to Step 8.
Go to Step 7.

STEP 7. Check harness between brake booster pressure sensor connector terminal and engine-ECU connector terminal BBPS.



  • Check output line for short circuit.

Q. Is the check result normal?

Replace the brake booster pressure sensor.
Repair or replace the connector, or repair the damaged harness wire.

STEP 8. Perform voltage measurement at engine-ECU connector



  • Disconnect engine-ECU connector, and connect special tool power plant ECU check harness (MB992110) to measure at connector for inspection.
  • Start up the engine and let it idle for several minutes.
  • Stop the engine, and turn the ignition switch to the ON position.
  • Depress the brake pedal several times.
  • Voltage between terminal engine-ECU BBPS line and body earth.
OK: Voltage is proportional to the brake pedal depression.

Q. Is the check result normal?

Go to Step 4.
Go to Step 9.

STEP 9. Check harness between brake booster pressure sensor connector terminal and engine-ECU connector terminal BBPS.



  • Check output line for open circuit and damage.

Q. Is the check result normal?

Go to Step 4.
Repair or replace the connector, or repair the damaged harness wire.