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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1074 (Engine Controls Diagnosis - 6.6L (LLY) (DTC P0653 To DTC P2228)) >> Diagnosis >> DTC P1093 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  If the fuel temperature is high enough to set DTC P0168, the fuel may be thin enough to cause this DTC to set.
  2. 4:  The engine will not start if the fuel leak is large enough.
  3. 5:  This step inspects for an inaccurate fuel rail pressure sensor.
  4. 6:  This step inspects for fuel leaks into the engine oil.
  5. 7:  This step inspects for a restriction in the fuel system between the fuel injection pump and the fuel tank.
  6. 8:  This test verifies 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. 9:  This step inspects 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. 10:  This step verifies to see if the fuel rail pressure sensor wiring and ECM are functioning normally.
  9. 12:  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.
DTC P1093

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module (ECM) 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 engine control module (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 16 
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?		 1.0-1.8 MPa Go to Step 6  Go to Step 10 
6  Inspect for fuel contamination. Refer to Contaminants-in-Fuel Diagnosis .
Did you find and correct the condition?		 - Go to Step 17  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 inches Go to Step 8  Go to Step 11 
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, inspect 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  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 inches Go to Diagnostic Aids Go to Step 11 
10 
  1. Disconnect the fuel rail pressure sensor. Refer to Fuel Rail Pressure (FRP) Sensor Replacement .
  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 15  Go to Step 14 
11 Replace the fuel filter. Refer to Fuel Filter Replacement .
Did you compete the replacement?		 - Go to Step 12  -
12 
  1. Ensure that the J 44638  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.
Does the vacuum measure less than or equal to the specified value?		 5 inches at idle
12 inches at high speed		 Go to Step 17  Go to Step 13 
13 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 17  -
14 Inspect 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 17  Go to Step 16 
15 Replace the fuel rail pressure sensor. Refer to Fuel Rail Pressure (FRP) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 17  -
16 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 17  -
17
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 18 
18 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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