Code No. P0191: Rail Pressure Sensor Range/Performance Problem
OPERATION
- 5 V power is supplied from the engine-ECU connector terminal FPS5 to the rail pressure sensor connector terminal.
- The rail pressure sensor connector terminal is earthed to the engine-ECU connector terminal FPSE.
- Sensor signals are input from the rail pressure sensor connector terminal to the engine-ECU connector terminal FPS.
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 JUDGEMENT
Check Condition
Judgement Criterion
- A difference between the objective and actual rail pressures exceeds 15 MPa, and the rail pressure sensor has an output voltage variation of 0.01 V or less.
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.
PROBABLE CAUSES
- Failed rail pressure sensor
- Harness damage in rail pressure sensor circuit or loose connector contact
- Failed suction control valve
- Failed engine-ECU
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STEP 1. Check suction control valve itself.
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- Check suction control valve itself (Refer to
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Q.
Is the check result normal?
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 Go to Step 2.
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 Replace the suction control valve.
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STEP 2. Check of damage in FPSE line between engine-ECU connector and rail pressure sensor connector.
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Q.
Is the check result normal?
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Go to Step 3.
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Repair the connector(s) or wiring harness.
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STEP 3. Check of damage in FPS5 line between engine-ECU connector and rail pressure sensor connector.
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Q.
Is the check result normal?
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Go to Step 4.
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Repair the connector(s) or wiring harness.
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STEP 4. Check of open circuit, short to earth, and damage in FPS line between engine-ECU connector and rail pressure sensor connector.
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Q.
Is the check result normal?
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Go to Step 5.
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Repair the connector(s) or wiring harness.
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STEP 5. Voltage measurement at rail pressure sensor connector (FPS line).
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(1)Use special tool test harness (MB991658) to connect connector, and measure at pick-up harness.
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(2)Engine: Idling (after warming up)
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(3)Check the voltage between the rail pressure sensor connector (FPS line) and body earth.
OK: 1.15 - 1.75 V
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Q.
Is the check result normal?
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Replace the engine-ECU.
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Replace the common rail assembly and fuel injection tubes.
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