Yukon Denali 4WD V8-6.0L Hybrid (2011)
Fuel Pressure: Testing and Inspection
Fuel System Diagnosis
Fuel System Diagnosis
Diagnostic Instructions
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Perform the Diagnostic System Check - Vehicle See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle prior to using this diagnostic procedure.
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Review Strategy Based Diagnosis See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis for an
overview of the diagnostic approach.
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Diagnostic Procedure Instructions See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
Circuit/System Description
The engine control module (ECM) supplies a high voltage signal to the fuel pump control module (FPCM) when the ECM detects that the ignition is on.
The high voltage signal from the ECM to the FPCM remains active for 2 seconds, unless the engine is in crank or run. While this signal is being
received, the FPCM closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel tank pump module in order to maintain the
desired fuel rail pressure.
Reference Information
Electrical Information Reference
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Circuit Testing See: Testing and Inspection/Component Tests and General Diagnostics/Circuit Testing/Circuit Testing
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Connector Repairs See: Testing and Inspection/Component Tests and General Diagnostics/Connector Repairs/Connector Repairs
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Testing for Intermittent Conditions and Poor Connections See: Testing and Inspection/Component Tests and General Diagnostics/Circuit
Testing/Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs See: Testing and Inspection/Component Tests and General Diagnostics/Wiring Repairs/Wiring Repairs
Scan Tool Reference
Control Module References See: Testing and Inspection/Programming and Relearningfor scan tool information
Special Tools
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CH-48027 Fuel Pressure Gauge
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J 37287 Fuel Line Shut-Off Adapters
Circuit/System Verification
Important:
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Repair all fuel system related DTCs before performing this diagnostic.
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Inspect the fuel system for damage or external leaks before proceeding.
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Verify that adequate fuel is in the fuel tank before proceeding.
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The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
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Before proceeding with this test review the User Manual CH 48027-5 for safety information and instructions.
1. Ignition OFF, open the hood to disable the Auto-Stop function. Refer to Hybrid Modes of Operation Description See: Hybrid Drive
Systems/Description and Operation/Hybrid Modes of Operation Description.
2. Ignition ON, verify the scan tool hood position parameter displays OPEN
‹› If the hood position does not display OPEN, refer to Diagnostic Trouble Code (DTC) List - Vehicle See: Computers and Control
Systems/Testing and Inspection/Diagnostic Trouble Code Descriptions/Diagnostic Trouble Code (DTC) List - Vehicle for DTC P254F.
3. Ignition OFF, all accessories OFF, install the CH-48027 . Refer to Fuel Pressure Gauge Installation and Removal See: Fuel Pressure Gauge
Installation and Removal.
4. Ignition ON, command the fuel pump Enable ON with a scan tool. Verify the fuel pressure is between 345-414 kPa (50-75 psi) and remains steady
for 5 minutes.
Circuit/System Testing
