P0191
DTC P0191
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P0191
-
Fuel Rail Pressure (FRP) Sensor Performance
Diagnostic Fault Information
Circuit/System Description
The fuel pressure sensor is located on the fuel line. The fuel pressure sensor monitors the fuel pressure in the fuel line. The fuel pump flow control module (FPCM) monitors the voltage signal from the fuel pressure sensor.
Conditions for Running the DTC
* The engine is running.
* DTC P0192, P0193, or P1255 are not active.
* DTC P0641 has not failed this ignition cycle.
* Fuel pump control is enabled and the fuel pump control state is normal.
* The engine has been running for at least 5 seconds.
Conditions for Setting the DTC
The FPCM does not detect a change in the fuel rail pressure of at least 30 kPa (4.4 psi).
Action Taken When the DTC Sets
DTC P0191 is a Type B DTC.
Conditions for Clearing the DTC
DTC P0191 is a Type B DTC.
Diagnostic Aids
Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.
Reference Information
Schematic Reference
Engine Controls Schematics (LS3) [1][2]Electrical DiagramsEngine Controls Schematics (LS9) [1][2]Electrical DiagramsEngine Controls Schematics (LS7) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Folding Top 5 Bow Lowered Switch (CM7)
Description and Operation
Fuel System Description (LS3 or LS7) Description and OperationFuel System Description (LS9) Description and Operation
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Testing
Note:
Verify that the fuel tank is not empty. Only perform this diagnostic if there is at least 2 gallons of fuel in the fuel tank. Clear the DTC, and start and run the engine. Verify that the DTC P0191 resets before proceeding with the circuit system testing. If the DTC does not reset, refer to diagnostic aids.
1. Ignition OFF, disconnect the harness connector at the fuel pressure sensor.
2. Ignition OFF, test for less than 15 ohms between the low reference circuit terminal 2 and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the fuel pump flow control module.
3. Ignition ON, test for 4.8-5.2 V between the fuel line pressure sensor 5 V reference circuit terminal 3 and ground.
• If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fuel pump flow control module.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the fuel pump flow control module.
4. Verify the scan tool 5 V reference is less than 1 V.
• If greater than the specified range, test the signal circuit terminal 1 for a short to voltage. If the circuit tests normal, replace the fuel pump flow control module.
5. Install a 3A fused jumper wire between the signal circuit terminal 1 and the 5 V reference circuit terminal 3. Verify the scan tool 5 V reference parameter is greater than 4.8 V.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fuel pump flow control module.
6. If all circuits test normal, replace the fuel pressure sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Fuel Pump Flow Control Module Replacement Fuel Pump Flow Control Module Replacement
* Fuel Tank Pressure Sensor Replacement Service and Repair
* Control Module References Control Module References for FPCM, replacement, setup, and programming