GM Service Manual Online
For 1990-2009 cars only

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 Descriptor

DTC P0093: Fuel System Large Leak Detected

Diagnostic Fault Information

Circuit

Short to Ground

Open

Short to Voltage

Fuel Rail Pressure Sensor 5-Volt Reference Circuit

P0192, P02E8, P0409, P0462, P0642, P2453, P2454, P2564

P0192

--

Fuel Rail Pressure Sensor Signal Circuit 1

P0192

P0193

P0193

Fuel Rail Pressure Sensor Signal Circuit 2

P0192

P0193

P0193

Fuel Rail Pressure Sensor Signal Circuit 1 and 2

P0192

P0193

P0193

Fuel Rail Pressure Sensor Ground Circuit

--

P0193

--

Typical Scan Tool Data

Actual Fuel Rail Pressure

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine Running

Parameter Normal Range: 25 MPa

Fuel Rail Pressure Sensor 5-Volt Reference Circuit

0.0 MPa

0.0 MPa

--

Fuel Rail Pressure Sensor Signal Circuit 1

0.0 MPa

246.6 MPa

246.6 MPa

Fuel Rail Pressure Sensor Signal Circuit 2

0.0 MPa

246.6 MPa

246.6 MPa

Fuel Rail Pressure Sensor Signal Circuit 1 and 2

0.0 MPa

246.6 MPa

246.6 MPa

Fuel Rail Pressure Sensor Ground Circuit

--

246.6 MPa

--

Circuit/System Description

The common rail fuel system is comprised of two fuel pressure sections: a suction side between the fuel tank and the fuel supply pump and a high-pressure side between the fuel supply pump and the fuel injectors. Fuel is drawn from the fuel tank via a feed pump, then pumped into the fuel rail by two plungers, all of which are internal to the fuel supply pump. This high pressure is regulated by the engine control module (ECM) using the fuel rail pressure (FRP) regulator dependant upon values from the FRP sensor attached to the fuel rail. If the ECM detects that the fuel pressure is lower than the desired value, this DTC will set. This most likely indicates some loss of fuel pressure or intermittently loss of fuel pressure by fuel leak from the high pressure side.

Conditions for Running the DTC

    • DTCs P0089, P0091, P0092, P0192, P0193, P0335, P0602, P0642, P0643, P0652 and P0653 are not set.
    • The battery voltage is between 10-16 volts.
    • The FRP regulator control mode is normal.
    • The engine is running.

Conditions for Setting the DTC

    • The ECM detects that the difference of the fuel leak quantity is larger than a threshold.
        OR
    • The ECM detects that the fuel rail pressure is dropped more than a threshold after an injection event compared with the previous injection.
        OR
    • The ECM detects that the fuel rail pressure is less than 18 MPa.

Action Taken When the DTC Sets

DTC P0093 is a Type A DTC.

Conditions for Clearing the DTC

DTC P0093 is a Type A DTC.

Diagnostic Aids

    • Air in fuel line will cause this DTC to set.
    • Inspect for any recent engine mechanical repairs. An incorrectly installed fuel rail pressure (FRP) sensor will cause this DTC to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

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

Special Tools

    • EN-47667 Fuel Pressure/Vacuum Gage Adapter
    • J 44638 Vacuum Gage

Circuit/System Verification

Verify the integrity of the fuel system and fuel rail pressure sensor by inspecting for the following conditions:

    • Damaged components
    • Loose or improper installation

Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Ignition OFF, inspect the high pressure side fuel line between the fuel supply pump and the fuel injectors for fuel leakage.
  2. If a fuel leak for fuel line is detected, repair or replace the fuel line.
  3. Ignition OFF, test for 3.24 MPa (200 RPM) of engine compression pressure.
  4. If less than 3.24 MPa (200 RPM), repair the engine compression issue.
  5. Start the engine. If any DTCs set, test and repair those DTCs.
  6. Ignition OFF, wait 2 minutes after observing the Actual Fuel Pressure parameter with a scan tool. The actual pressure should be 0 MPa with the engine not running at operating temperature.
  7. If the pressure difference between the actual and desired pressure are more than 2 MPa, replace the fuel rail pressure sensor.
  8. Start the engine. Inspect the fuel line between the fuel tank and the fuel injectors for fuel leakage.
  9. If a fuel leak for the fuel line is detected, repair or replace the fuel line.
  10. Connect the suction side fuel pressure adapter EN-47667 with fuel vacuum/pressure gage assembly J 44638 in series with the filter housing and the disconnected fuel hose. Bleed the fuel system by priming the priming pump until it becomes firm, then crank over the engine for a maximum of 5 seconds. Repeat as necessary until the engine starts.
  11. Let the engine run at idle for at least 1 minute. Monitor the fuel vacuum/pressure gage while holding the engine speed higher than 2,500 RPM for a minimum of 1 minute.
  12. Observe the fuel vacuum/pressure with a pressure gage. The vacuum/pressure gage ever indicate a larger vacuum than 5 in Hg.
  13. If vacuum/pressure gage ever indicate a larger vacuum than the specified amount during the test, repair or replace the fuel line/fuel filter/fuel tank.
  14. Test the injector for injector balance test with a scan tool.
  15. If engine noise does not change, replace the fuel injector.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Fuel Filter Replacement
    •  Fuel Injector Replacement
    •  Fuel Pressure Regulator Replacement
    •  Control Module References for ECM replacement, setup, and programming