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SMU - Revised DTC P0093 or DTC P1093

Subject:Revised DTC P0093 or DTC P1093 Diagnostic Tables

Models:2001-2004 Chevrolet Silverado
2003-2004 Chevrolet Kodiak
2001-2004 GMC Sierra
2003-2004 GMC TopKick
with 6.6L Diesel Engine (VIN 1 - RPO LB7)


This bulletin is being issued to revise DTC P0093 (2001) and DTC P1093 (2002-2004) diagnostic tables in the Engine Controls sub-section of the Service Manual. Please replace the current information in the Service Manual with the following information.

The following information has been updated within SI. If you are using a paper version of this Service Manual, please make a reference to this bulletin on the affected page.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. If the fuel temperature is high enough to set DTC P0168, the fuel may be thin enough to cause this DTC to set.

    2.

  2. The engine will not start if the fuel leak is large enough.

    3.

  3. This step checks for an inaccurate fuel rail pressure sensor.

  4. This step checks for fuel leaks into the engine oil.

    5.

  5. This step checks for a restriction in the fuel system between the fuel injection pump and the fuel tank.

    6.

  6. This test checks to see if the fuel injection pump is able to supply maximum fuel pressure at idle. The fuel injection pump should be able to create 145-158 MPa at idle. At higher ambient temperatures, the fuel pressure will be lower, but still more than 145 MPa.

    7.

  7. This step checks for a restriction in the fuel system between the fuel injection pump and the fuel tank that may only cause symptoms at higher engine speed and load conditions.

    8.

  8. This step checks to see if the fuel rail pressure sensor wiring and ECM are functioning normally.

    9.

  9. If the vacuum is still too high in the fuel supply system after replacing the fuel filter, there is a restriction in the fuel supply lines or sending unit in the fuel tank.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check-Engine Controls

2

Is DTC P0168 or P0090 also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

    Important: Failure to wait until there is no ECM communications with the scan tool will result in misdiagnosis.

  1. Turn OFF the ignition for 30 seconds.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the FRP Regulator Command parameter with a scan tool.

Is the FRP Regulator Command more than the specified value?

20%

Go to Step 4

Go to Step 17

4

Attempt to start the engine.

Does the engine start and idle?

--

Go to Step 5

Go to Engine Cranks but Does Not Run

5
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the Actual Fuel Rail Pressure parameter with a scan tool.

Is the Actual Fuel Rail Pressure Parameter within the specified range?

1.1-1.4 MPa

Go to Step 6

Go to Step 11

6

Check the engine oil for fuel contamination. Refer to Fuel in Engine Oil in Engine Mechanical.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 7

7
  1. Install the J 44638 Vacuum Gage on the fuel fitting located on the right side front of the engine.
  2. Start and run the engine at idle.
  3. Observe the vacuum gage while increasing RPM slowly to wide open throttle (WOT) in park or neutral.

Does the vacuum measure less than the specified value through the entire RPM range?

5 in

Go to Step 8

Go to Step 12

8
  1. Start and idle the engine until the idle speed drops to 680 RPM.
  2. Command the fuel pressure control to 160 MPa with a scan tool.
  3. Observe the Actual Fuel Rail Pressure parameter with a scan tool.

Is the Actual Fuel Rail Pressure parameter more than the specified value?

145 MPa

Go to Step 9

Go to Fuel System Diagnosis-High Pressure Side

9

Important: If the fuel temperature is near 121°C (250°F) during the duplication of the complaint (or in the Failure Records for this DTC), check for a restriction in the fuel cooler air flow or the fuel heater always ON. Refer to Fuel Heater Always On.

  1. Ensure that the J 44638 Vacuum Gage is still installed on the engine.
  2. Operate the vehicle within the conditions for which the customer complaint occurs.

Does the vacuum measure less than the specified value through the entire operating range?

12 in

Go to Step 10

Go to Step 12

10

Ask the customer if there has been a power-enhancing device attached to the fuel rail pressure sensor circuits.

What was the customers answer?

--

Go to Step 18

Go to Fuel System Diagnosis-High Pressure Side

11
  1. Disconnect the fuel rail pressure sensor.
  2. Observe the Actual Fuel Rail Pressure with a scan tool.

Does the Actual Fuel Rail Pressure measure more than the specified value?

175 MPa

Go to Step 16

Go to Step 15

12

Replace the fuel filter. Refer toFuel Filter Replacement .

Did you compete the replacement?

--

Go to Step 13

--

13
  1. Ensure that the J 44638 Vacuum Gage is still installed on the engine.
  2. Start and run the engine under the conditions for which the high vacuum occurred in the previous test.
  3. Observe the J 44638 .

Does the vacuum measure less than or equal to the specified value?

5 in at idle or 12 in at high speed

Go to Step 18

Go to Step 14

14

Repair the restriction in the fuel supply lines between the fuel tank and the fuel injection pump. Refer to Fuel System Diagnosis.

Did you complete the repair?

--

Go to Step 18

--

15

Check the fuel rail pressure sensor signal circuit for a short to ground. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 17

16

Replace the fuel rail pressure sensor. Refer to Fuel Rail Pressure (FRP) Sensor Replacement .

Did you complete the replacement?

--

Go to Step 18

--

17

Replace the ECM. Refer to Engine Control Module (ECM) Replacement .

Did you complete the replacement?

--

Go to Step 18

--

18
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 19

Go to Step 2

19

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK