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DTC P0191: Fuel Rail Pressure Circuit Range/Performance Problem
 
 
 
 
CIRCUIT OPERATION
Refer to DTC P0192 - Fuel Rail Pressure Circuit Low Input , DTC P0628 - Fuel Pump (High Pressure) Control Circuit Low Input .
 
 
TECHNICAL DESCRIPTION
ECM checks the fuel rail pressure sensor output signal characteristics for abnormal conditions.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC set in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Not applicable
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Conditions
  • Engine starting sequence was completed.
  • Battery positive voltage is higher than 10 volts.
  • Fuel rail pressure at monitor start is within the specified range.
Judgment Criterion
  • During the drive cycle, the ECM performs monitoring with the total ignition of 50.
  • The absolute value of the difference between the maximum fuel rail pressure and the minimum fuel rail pressure has continued to be less than the specified value.
Check Conditions
  • Engine starting sequence was completed.
  • Battery positive voltage is higher than 10 volts.
  • Fuel rail pressure at monitor start is higher than the specified value.
  • Fuel rail pressure at monitor start is higher than target fuel rail pressure.
  • Fuel injection mode is not MFI-mode.
Judgment Criterion
  • During the drive cycle, the ECM performs monitoring with the total ignition of 30.
  • The absolute value of the difference between the maximum fuel rail pressure and the minimum fuel rail pressure has continued to be less than the specified value.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • While prohibiting the operation of the injector (high pressure), carry out the control by the injector operation only.
  • Torque is restricted.
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
  • Fuel rail pressure sensor failed.
  • Injector (high pressure) failed.
  • Fuel pump (high pressure) failed.
  • Open or Shorted fuel rail pressure sensor circuit, harness damage or connector damage.
  • High-pressure fuel line clogged.
  • Fuel rail (high pressure) failed.
  • ECM failed.

 
 
DIAGNOSIS
noteThis DTC can be output for an air penetration in the fuel line due to lack of fuel. Therefore, bleed air from the fuel line after the fuel supply, and delete the DTC through scan tool (M.U.T.-IIISE).
Required Special Tool:
  • MB991709: Test Harness
STEP 1. Using scan tool (M.U.T.-IIISE), read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
(1) Connect scan tool (M.U.T.-IIISE). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) .
(2) Turn the ignition switch to the "ON" position.
(3) Set scan tool (M.U.T.-IIISE), read the DFI and MFI-DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the diagnostic trouble code other than P0191 set?
Refer to Diagnostic Trouble Code Chart .
Go to Step 2.
 
STEP 2. Check of open circuit, short circuit and harness damage in HFP5 line between fuel rail pressure sensor connector and ECM connector.
Is the harness wire in good condition?
Go to Step 3.
Repair the connector(s) or wiring harness. Then go to Step 11.
 
STEP 3. Check of short circuit and harness damage in HFPS line between fuel rail pressure sensor connector and ECM connector.
Is the harness wire in good condition?
Go to Step 4.
Repair the connector(s) or wiring harness. Then go to Step 11.
 
STEP 4. Check of short circuit and harness damage in HFPG line between fuel rail pressure sensor connector and ECM connector.
Is the harness wire in good condition?
Go to Step 5.
Repair the connector(s) or wiring harness. Then go to Step 11.
 
STEP 5. Measure the sensor output voltage at fuel rail pressure sensor connector.
(1) Using test harness special tool MB991709 to connect connector, and measure at pick-up harness.
(2) Measure the voltage between terminal HFPS line and ground.
  • The output voltage of the fuel pressure sensor changes before starting and after starting.
Is the measured voltage normal?
Go to Step 6.
Replace the fuel rail (high pressure) (integrated with fuel rail pressure sensor). Then go to Step 11.
 
STEP 6. Check of harness damage in HFP+ line between fuel pump (high pressure) connector and ECM connector.
Is the harness wire in good condition?
Go to Step 7.
Repair the connector(s) or wiring harness. Then go to Step 11.
 
STEP 7. Check of harness damage in HFP- line between fuel pump (high pressure) connector and ECM connector.
Is the harness wire in good condition?
Go to Step 8.
Repair the connector(s) or wiring harness. Then go to Step 11.
 
STEP 8. Check the trouble symptoms.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0191 set?
Replace the fuel rail (high pressure), high-pressure fuel line and injector (high pressure). Then go to Step 9.
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
 
STEP 9. Check the trouble symptoms.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0191 set?
Replace the fuel pump (high pressure). Then go to Step 10.
The inspection is complete.
 
STEP 10. Check the trouble symptoms.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0191 set?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 11.
The inspection is complete.
 
STEP 11. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0191 set?
Retry the troubleshooting.
The inspection is complete.