Code No. P0192: Rail Pressure Sensor Circuit Low Input




OPERATION



  • A power voltage of 5 V is applied to the rail pressure sensor power terminal (terminal No. 1) from the engine-ECU (terminal No. 81) and earthed to the engine-ECU (terminal No. 76) from the rail pressure sensor (terminal No. 3).
  • The sensor signal is inputted to the engine-ECU (terminal No. 56) from the rail pressure sensor output terminal (terminal No. 2).

FUNCTION



  • The rail pressure sensor converts the rail pressure into a voltage signal and inputs the signal to the engine-ECU.
  • In response to the signal, the engine-ECU corrects the fuel injection quantity.

TROUBLE JUDGMENT


Check Conditions
  • Battery positive voltage is 8 - 16 V
  • 2 seconds later after the ignition switch has been in "ON" position or the engine has started up.
Judgment Criterion
  • The rail pressure sensor output voltage is 0.70 V or less for 0.5 second.

PROBABLE CAUSES



  • Failed rail pressure sensor
  • Open/short circuit in rail pressure sensor circuit or loose connector contact

  • Failed engine-ECU

DIAGNOSIS PROCEDURE

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

  • Refer to Data List Reference Table .

  1. Item 63: Rail 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. Connector check: A-44 rail pressure sensor connector

Q. Is the check result normal?

Go to Step 3 .

Repair or replace the connector.

STEP 3. 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.
  • Ignition switch: ON
  • Voltage between terminal No. 1 and earth.
OK: 4.9 - 5.1 V

Q. Is the check result normal?

Go to Step 9 .

Go to Step 4 .

STEP 4. Perform voltage measurement at C-105 engine-ECU connector.


  • Measure engine-ECU terminal voltage.
  • Ignition switch: ON
  • Voltage between terminal No. 81 and earth.
OK: 4.9 - 5.1 V

Q. Is the check result normal?

Go to Step 8 .

Go to Step 5 .

STEP 5. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 6 .

Repair or replace the connector.

STEP 6. Check harness between A-44 (terminal No. 1) rail pressure sensor connector and C-105 (terminal No. 81) engine-ECU connector.


note Before checking harness, check intermediate connector A-131, and repair if necessary.

  • Check power supply line for short circuit.

Q. Is the check result normal?

Go to Step 7 .

Repair the damaged harness wire.

STEP 7. M.U.T.-III data list

  • Refer to Data List Reference Table .

  1. Item 63: Rail 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. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - How to Perform Chassis Number Writing ). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns ).

STEP 8. Connector check: C-105 engine-ECU connector


Q. Is the check result normal?


    Check intermediate connector A-131, and repair if necessary. If intermediate connector is normal, check and repair harness between A-44 (terminal No. 1) rail pressure sensor connector and C-105 (terminal No. 81) engine-ECU connector.

    • Check power supply line for open circuit and damage.

Repair or replace the connector.

STEP 9. Perform resistance measurement at A-44 rail pressure sensor connector.


  • Disconnect and measure at harness side.
  • Ignition switch: ON
  • Resistance between terminal No. 3 and earth.
OK: Continuity (2 Ω or less)

Q. Is the check result normal?

Go to Step 12 .

Go to Step 10 .

STEP 10. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 11 .

Repair or replace the connector.

STEP 11. Check harness between A-44 (terminal No. 3) rail pressure sensor connector and C-105 (terminal No. 76) engine-ECU connector.


note Before checking harness, check intermediate connector A-131, and repair.

  • Check earthing line for damage.

Q. Is the check result normal?

Go to Step 7 .

Repair the damaged harness wire.

STEP 12. 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: Idle (after warning up)
  • Voltage between terminal No. 2 and earth.
OK: 1.15 - 1.75 V

Q. Is the check result normal?

Go to Step 15 .

Go to Step 13 .

STEP 13. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 14 .

Repair or replace the connector.

STEP 14. Check harness between A-44 (terminal No. 2) rail pressure sensor connector and C-105 (terminal No. 56) engine-ECU connector.


note Before checking harness, check intermediate connector A-131, and repair if necessary.

  • Check output line for short circuit.

Q. Is the check result normal?

Replace the common rail assembly.

Repair the damaged harness wire.

STEP 15. Perform voltage measurement at C-105 engine-ECU connector.


  • Measure engine-ECU terminal voltage.
  • Engine: Idle (after warning up)
  • Voltage between terminal No. 56 and earth.
OK: 1.15 - 1.75 V

Q. Is the check result normal?

Go to Step 17 .

Go to Step 16 .

STEP 16. Connector check: C-105 engine-ECU connector


Q. Is the check result normal?


    Check intermediate connector A-131, and repair if necessary. If intermediate connector is normal, check and repair check harness between A-44 (terminal No. 2) rail pressure sensor connector and C-105 (terminal No. 56) engine-ECU connector.

    • Check output line for open circuit and damage.

Repair or replace the connector.

STEP 17. Connector check: C-105 engine-ECU connector

Q. Is the check result normal?

Go to Step 7 .

Repair or replace the connector.