P0191 – Rail Pressure Sensor Range-Performance Problem MMC L200 IV



OPERATION

  • 5 V power is supplied from the engine-ECU (terminal No. 70) to the rail pressure sensor (terminal No. 1).
  • The rail pressure sensor (terminal No. 3) is earthed to the engine-ECU (terminal No. 88).
  • Sensor signals are input from the rail pressure sensor (terminal No. 2) to the engine-ECU (terminal No. 64).

  • FUNCTION

  • The engine-ECU monitors the signals input from the rail pressure sensor.
  • Based on these signals, the engine-ECU checks the rail pressure sensor for errors.

  • TROUBLE JUDGMENT

  • Engine is running.
  • A difference between the objective and actual rail pressures exceeds 15 MPa for 0.5 second, and the rail pressure sensor has an output voltage variation of 0.01 V or less.

  • PROBABLE CAUSES

  • Failed rail pressure sensor
  • Failed suction control valve
  • Fuel line blocked
  • Failed engine-ECU

  • DIAGNOSIS PROCEDURE

    STEP 1. Check suction control valve itself.

    Q. Is the check result normal?

    STEP 2. Connector check: A-44 rail pressure sensor connector.

    Q. Is the check result normal?

    STEP 3. Connector check: C-105 engine-ECU connector

    Q. Is the check result normal?

    STEP 4. Check harness between A-44 (terminal No. 3) rail pressure sensor connector and C-105 (terminal No. 88) engine-ECU connector.

  • Check earthing line for damage.
  • Q. Is the check result normal?

    STEP 5. Check harness between A-44 (terminal No. 1) rail pressure sensor connector and C-105 (terminal No. 70) engine-ECU connector.

  • Check power supply line for damage.
  • Q. Is the check result normal?

    STEP 6. Check harness between A-44 (terminal No. 2) rail pressure sensor connector and C-105 (terminal No. 64) engine-ECU connector.

  • Check output line for damage.
  • Q. Is the check result normal?

    STEP 7. Perform voltage measurement at A-44 rail pressure sensor connector.

  • Use special tool test harness (MB991658) to connect connector, and measure at pick-up harness.
  • Engine: Idling (after warning up)
  • Voltage between terminal No. 2 and earth.
  • Q. Is the check result normal?

    Author: admin