Buick Regal: DTC P0191 or P0192

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0191

Fuel Rail Pressure Sensor Performance

DTC P0192

Fuel Rail Pressure Sensor Circuit Low Voltage

Diagnostic Fault Information

Circuit/System Description

The fuel rail pressure sensor transmits fuel pressure and temperature information by serial data using the Society of Automotive Engineers (SAE) J2716 Single Edge Nibble Transmission (SENT) protocol. The fuel rail pressure sensor internal microprocessor allows 4 separate sensor outputs from one 3 wire sensor. The engine control module (ECM) supplies the fuel rail pressure sensor with a 5 V reference circuit, a low reference circuit, and an asynchronous signal/serial data circuit. The asynchronous signal means communication is only going from the fuel rail pressure sensor to the ECM.

Conditions for Running the DTC

P0191 - Condition 1

• 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 250 kPa (36 PSI).
• The Accelerator Pedal Position is 0% for 2.5 s.
• The engine is running for greater than 30 s.

P0191 - Condition 2 and 3

• The engine is not cranking.
• The ignition voltage is greater than 11 V.
• The engine speed is between 1, 000 - 3, 000 RPM.
• The vehicle speed is greater than or equal to 35 km/h (22 MPH).
• The low side fuel pressure is greater than or equal to 250 kPa (36 PSI).
• The Desired Fuel Rail Pressure is between 4 - 6 MPa (580 - 870 PSI).
• The Accelerator Pedal Position is greater than or equal to 10%.
• The engine is running for greater than 30 s.

P0191 - Condition 4

• DTC P0016, P0017, P0090, P0091, P0092, P00C8, P00C9, P00CA, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0119, 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, P0628, P0697, P06A3, P0722, P0723, P1248, P1249, P124A, P124B, P1682, P2122, P2123, P2127, P2128, P2135, P2138, 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.
• The barometric (BARO) pressure is greater than 70 kPa.
• The intake air temperature (IAT) is warmer than -20ºC (-4ºF).

P0192

• The engine is running.
• The ignition voltage is greater than 11 V.
• The DTCs run continuously within the enabling conditions.

Conditions for Setting the DTC

P0191 - Condition 1

The difference between the low side fuel pressure and the high side fuel pressure is less than or equal to -1 MPa (-145 PSI) or greater than or equal to 1 MPa (145 PSI) with the high pressure fuel pump actuator commanded OFF. The condition exists for greater than 3 s.

P0191 - Condition 2

The difference between the relief pressure and the measured high pressure is less than or equal to -1.6 MPa (-232 PSI) with the high pressure fuel pump actuator commanded ON. The condition exists for greater than 2 s.

P0191 - 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 1.6 MPa (232 PSI) with the high pressure fuel pump actuator commanded ON. The condition exists for greater than 3 s.

P0191 - 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 30 s with the engine running or greater than 10 s with the engine cranking.

P0192

The ECM detects that the fuel rail fuel pressure sensor signal voltage is low for greater than 5 s.

Action Taken When the DTC Sets

• DTCs P0191, P0192, are Type A DTCs.
• A message center or an indicator may display Reduced Engine Power.

Conditions for Clearing the DTC

• DTCs P0191, P0192 are Type A DTCs.

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

Powertrain Component View

Powertrain Component Views

Description and Operation

Fuel System Description

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition On.

2. Verify DTC P0641 is not set.

• If the DTC is set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

• Go to next step: If the DTC is not set

3. Engine idling.

4. Verify DTC P0191 or P0192 is not set.

• If any of the DTCs are set

Refer to Circuit/System Testing.

• Go to next step: If none of the DTCs are set

5. 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.

6. Verify the DTC does not set.

• If the DTC sets

Refer to Circuit/System Testing.

• Go to next step: If the DTC does not set

7. All OK.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the fuel injector multi-way harness connector X160. It may take up to 2 mins for all vehicle systems to power down.

NOTE: Testing for steps 2 through 7 is performed on the ECM side of the multi-way harness connector.

2. Test for less than 5 Ω between the low reference circuit terminal 5 and ground.

• If 5 Ω or greater

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: If less than 5 Ω

3. Ignition On.

4. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 11 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• If greater than 5.2 V

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition On.
2. Test for less than 1 V between the 5 V reference circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 Engine Control Module.

• Go to next step: If between 4.8 - 5.2 V

5. Verify the scan tool Fuel Rail Pressure Sensor voltage parameter is less than 0.02 V.

• If 0.02 V or greater

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition On.
2. Test for less than 1 V between the signal circuit terminal 12 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 Engine Control Module.

• Go to next step: If less than 0.02 V

6. Install a 3 A fused jumper wire between the signal circuit terminal 12 and the 5 V reference circuit terminal 11.

7. Verify the scan tool Fuel Rail Pressure Sensor voltage parameter is greater than 4.96 V.

• If 4.96 V or less

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit terminal 12 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: If greater than 4.96 V

8. Connect the fuel injector multi-way harness connector X160.

9. Disconnect the B47B Fuel Rail Pressure Sensor connector.

NOTE: Testing for steps 11 through 17 is performed at the fuel rail fuel pressure sensor connector.

10. Test for less than 5 Ω between the low reference circuit terminal 1 and ground.

• If 5 Ω or greater

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: If less than 5 Ω

11. Ignition On.

12. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 3 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• If greater than 5.2 V

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition On.
2. Test for less than 1 V between the 5 V reference circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 Engine Control Module.

• Go to next step: If between 4.8 - 5.2 V

13. Ignition On.

14. Verify the scan tool Fuel Rail Pressure Sensor voltage parameter is less than 0.02 V.

• If 0.02 V or greater

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition On.
2. Test for less than 1 V between the signal circuit terminal 2 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 Engine Control Module.

• Go to next step: If less than 0.02 V

15. Install a 3 A fused jumper wire between the signal circuit terminal 2 and the 5 V reference circuit terminal 3.

16. Verify the scan tool Fuel Rail Pressure Sensor voltage parameter is greater than 4.96 V.

• If 4.96 V or less

1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit terminal and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 Engine Control Module.

• Go to next step: If greater than 4.96 V

17. Replace the B47B Fuel Rail Pressure Sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• Fuel Injection Fuel Rail Fuel Pressure Sensor Replacement
• Control Module References for ECM replacement, setup, and programming

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