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. 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 0.70 V or less for 0.5 second.

PROBABLE CAUSES

Failed rail pressure sensor
Open/short 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

Refer to Data List Reference Table .

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. 70 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. 70) 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 .

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 - Precautions Before Service - 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

). After registering the injector identification code, the vehicle equipped with the DPF carries out the forcible DPF regeneration. (Refer to GROUP 17 - Emission Control - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration

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

Q. Is the check result normal?

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 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 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. 88) engine-ECU connector.

note

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

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. 64) 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. 64 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 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.