Code No. P0193: Rail Pressure Sensor Circuit High 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. 70) and earthed to the engine-ECU (terminal No. 88) from the rail pressure sensor (terminal No. 3).
The sensor signal is inputted to the engine-ECU (terminal No. 64) 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 4.85 V or more.

FAIL-SAFE AND BACKUP FUNCTION

The rail pressure is controlled in the range between 50 and 100 MPa.
The fuel injection amount is restricted (Output restriction).
The open angle of the accelerator pedal is restricted.
The throttle valve is closed (Fixed opening degree).
The EGR control is stopped (fully closed).
The DPF regeneration is prohibited.
The AS&G control is prohibited.

PROBABLE CAUSES

Failed rail pressure sensor
Open circuit or harness damage in rail pressure sensor circuit or loose connector contact
Failed engine-ECU

DIAGNOSIS PROCEDURE

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

Data list reference table (Refer to ).

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: B-33 rail pressure sensor

Q. Is the check result normal?

	Go to Step 3 .

	Repair or replace the connector.

STEP 3. Perform voltage measurement at B-33 rail pressure sensor connector.

Disconnect connector, and measure at harness side.
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 7 .

	Go to Step 4 .

STEP 4. Connector check: B-39 engine-ECU connector

Q. Is the check result normal?

	Go to Step 5 .

	Repair or replace the connector.

STEP 5. Check harness between B-33 (terminal No. 1) rail pressure sensor connector and B-39 (terminal No. 70) engine-ECU connector.

Check power supply line for open/short circuit.

Q. Is the check result normal?

	Go to Step 6 .

	Repair the damaged harness wire.

STEP 6. M.U.T.-III data list

Data list reference table (Refer to ).

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.

STEP 7. Perform resistance measurement at B-33 rail pressure sensor connector.

Disconnect connector, and measure at harness side.
Resistance between terminal No. 3 and earth.

OK: Continuity (2 Ω or less)

Q. Is the check result normal?

	Go to Step 10 .

	Go to Step 8 .

STEP 8. Connector check: B-39 engine-ECU connector

Q. Is the check result normal?

	Go to Step 9 .

	Repair or replace the connector.

STEP 9. Check harness between B-33 (terminal No. 3) rail pressure sensor connector and B-39 (terminal No. 88) engine-ECU connector.

Check earthing line for open circuit and damage.

Q. Is the check result normal?

	Go to Step 14 .

	Repair the damaged harness wire.

STEP 10. Connector check: B-39 engine-ECU connector

Q. Is the check result normal?

	Go to Step 11 .

	Repair or replace the connector.

STEP 11. Check harness between B-33 (terminal No. 1) rail pressure sensor connector and B-39 (terminal No. 70) engine-ECU connector.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 12 .

	Repair the damaged harness wire.

STEP 12. Check harness between B-33 (terminal No. 2) rail pressure sensor connector and B-39 (terminal No. 64) engine-ECU connector.

Check output line for open circuit and damage.

Q. Is the check result normal?

	Go to Step 13 .

	Repair the damaged harness wire.

STEP 13. Voltage measurement at B-33 rail pressure sensor connector.

Disconnect connector, and measure at sensor side.
With the special tool test harness (MB991658) bridge only the mating terminals of No. 1 and No. 3 of the disconnected connector.
Ignition switch: ON
Voltage between terminal No. 2 and earth.

OK: 0.85 V or more

Q. Is the check result normal?

	Go to Step 14 .

	Replace the rail pressure sensor.

STEP 14. M.U.T.-III data list

Data list reference table (Refer to ).

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.