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 Descriptors
DTC P0191
- Fuel Rail Pressure Sensor Performance
Diagnostic Fault Information
Circuit/System Description
The fuel rail fuel pressure sensor detects fuel pressure within the fuel rail. The engine control module (ECM) provides a 5 V reference voltage on the 5 V reference circuit and ground on the low reference circuit. The ECM receives a varying signal voltage on the signal circuit. The ECM monitors the voltage on the fuel rail fuel pressure sensor circuits. When the fuel pressure is high, the signal voltage is high. When the fuel pressure is low, the signal voltage is low.
Conditions for Running the DTC
Condition 1
* DTC P0016, P0017, P0068, P0090, P0091, P0092, P00C8, P00C9, P00CA, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0128, P0192, P0193, P0201, P0202, P0203, P0204, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0300, P0301, P0302, P0303, P0304, P0335, P0336, P0340, P0341, P0351-P0354, P0365, P0366, P0506, P0507, P0627, P0628, P0629, P0722, P0723, P1248, P1249, P124A, P124B, P1682, P16F3, P2101, P2122, P2123, P2127, P2128, P2135, P2147, P2148, P2150, P2151, P2153, P2154, P2156, P2157 is not set.
* The engine is not cranking.
* The ignition voltage is greater than 11 V.
* The vehicle speed is less than or equal to 1 km/h (0.62 mph).
* The low side fuel pressure is greater than or equal to 275 kPa (40 psi).
* The Accelerator Pedal Position is 0 percent for 12.5 s.
* DTC P0191 runs continuously when the above conditions have been met.
Condition 2 and 3
* DTC P0016, P0017, P0068, P0090, P0091, P0092, P00C8, P00C9, P00CA, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0128, P0192, P0193, P0201, P0202, P0203, P0204, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0300, P0301, P0302, P0303, P0304, P0335, P0336, P0340, P0341, P0351-P0354, P0365, P0366, P0506, P0507, P0627, P0628, P0629, P0722, P0723, P1248, P1249, P124A, P124B, P1682, P16F3, P2101, P2122, P2123, P2127, P2128, P2135, P2147, P2148, P2150, P2151, P2153, P2154, P2156, P2157 is not set.
* The engine is not cranking.
* The ignition voltage is greater than 11 V.
* The engine speed is between 1,000-2,200 RPM.
* The vehicle speed is greater than or equal to 45 km/h (27.96 mph).
* The low side fuel pressure is greater than or equal to 275 kPa (40 psi).
* The Desired Fuel Rail Pressure is between 7-8 MPa (1,015-1,160 psi).
* DTC P0191 runs continuously when the above conditions have been met.
Condition 4
* DTC P0016, P0017, P0068, P0090, P0091, P0092, P00C8, P00C9, P00CA, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0128, P0192, P0193, P0201, P0202, P0203, P0204, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0300, P0301, P0302, P0303, P0304, P0335, P0336, P0340, P0341, P0351-P0354, P0365, P0366, P0506, P0507, P0627, P0628, P0629, P0722, P0723, P1248, P1249, P124A, P124B, P1682, P16F3, P2101, P2122, P2123, P2127, P2128, P2135, P2147, P2148, P2150, P2151, P2153, P2154, P2156, P2157 is not set.
* The engine is not cranking.
* The vehicle speed is greater than or equal to 30 km/h (18.64 mph).
* The engine speed is greater than or equal to 2,000 RPM.
* DTC P0191 runs continuously when the above conditions have been met.
Conditions for Setting the DTC
Condition 1
The difference between the low side fuel pressure and the high side fuel pressure is less than or equal to -0.65 MPa (-94 psi) or greater than or equal to 0.6 MPa (87 psi) with the high pressure fuel pump actuator commanded OFF. The condition exists for greater than 3 s.
Condition 2
The difference between the relief pressure and the measured high pressure is less than or equal to -5 MPa (-725 psi) with the high pressure fuel pump actuator commanded ON. The condition exists for greater than 2 s.
Condition 3
The difference between the commanded high pressure and the measured high pressure is greater than or equal to 3 MPa (435 psi) and the modeled injection pressure is greater than or equal to 3 MPa (435 psi) with the high pressure fuel pump actuator commanded ON. The condition exists for greater than 3 s.
Condition 4
The difference between the measured maximum high pressure and the measured minimum high pressure is less than or equal to 0.1 MPa (14.5 psi) with the high pressure fuel pump actuator commanded ON. The condition exists for greater than 60 s.
Action Taken When the DTC Sets
* DTC P0191 is a Type A DTC.
* A message center or an indicator may display Reduced Engine Power.
Conditions for Clearing the DTC
DTC P0191 is a Type A DTC.
Diagnostic Aids
A condition with the fuel tank fuel pump module or the fuel pump control module may set this DTC.
Reference Information
Schematic Reference
Engine Controls Schematics (LEA) Electrical Diagrams
Connector End View Reference
Component Connector End Views Outside Rearview Mirror - Driver
Description and Operation
Fuel System Description Fuel System Description
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 Verification
1. Observe the scan tool DTC information, verify DTC P0627, P0628, P0629, P0641, P069E or U0109 is not set.
• If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. Engine idling, observe the scan tool Fuel Rail Pressure Sensor parameter. The pressure should be approximately 2.96-3.24 MPa (429-470 psi).
3. Engine idling, the scan tool Fuel Rail Pressure Sensor should be close to the scan tool Desired Fuel Rail Pressure. As the engine speed increases, the Desired Fuel Rail Pressure and the Fuel Rail Pressure Sensor should closely match each other.
4. Move related harnesses/connectors of the B47B fuel rail fuel pressure sensor and verify the engine does not stumble, stall, or change engine speed.
• If the engine stumbles, stalls, or changes engine speed, test or repair the suspected harness or connection.
5. Observe the DTC information with a scan tool, DTC P0191 should not set.
6. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, disconnect the fuel injector multi-way harness connector X160.
Note: Testing for steps 2 through 5 is performed on the ECM side of the multi-way harness connector.
2. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohms between the low reference circuit terminal 5 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 K20 ECM.
3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 11 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 K20 ECM.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
4. Ignition ON, verify the scan tool Fuel Rail Pressure Sensor voltage parameter is less than 0.02 V.
• If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
5. Connect a 3 A fused jumper wire between the signal circuit terminal 12 and the 5 V reference circuit terminal 11. Verify the scan tool Fuel Rail Pressure Sensor Voltage parameter is greater than 4.96 V.
• If less than the specified value, test the signal circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the K20 ECM.
6. Ignition OFF, remove the intake manifold.
7. Connect the fuel injector multi-way harness connector X160.
Note: Testing for steps 9 through 12 is performed at the fuel rail fuel pressure sensor connector.
8. Disconnect the B47B fuel rail fuel pressure sensor connector.
9. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal C and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance.
10. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal A 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 greater than the specified range, test the 5 V reference circuit for a short to voltage.
11. Ignition ON, verify the scan tool Fuel Rail Pressure Sensor voltage parameter is less than 0.02 V.
• If greater than the specified value, test the signal circuit for a short to voltage.
12. Connect a 3 A fused jumper wire between the signal circuit terminal B and the 5 V reference circuit terminal A. Verify the scan tool Fuel Rail Pressure Sensor voltage parameter is greater than 4.96 V.
• If less than the specified value, test the signal circuit for an open/high resistance or a short to ground.
13. If all circuits test normal, replace the B47B fuel rail fuel pressure sensor.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement
* Control Module References Control Module References for ECM replacement, setup, and programming