Yukon 4WD V8-5.3L (2008)
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Restricted or plugged strainer
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Stuck or binding fuel level float
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Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
Important: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel
pressure should stabilize and remain constant.
1. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
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If the fuel pressure decreases more than the specified value, perform the following procedure:
1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief (With CH 48027) Fuel Pressure Relief (Without CH 48027).
2. Install the J 37287 between the fuel feed pipe and the fuel rail.
3. Open the valve on the J 37287.
4. Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the fuel pressure gage.
5. Close the valve on the J 37287.
6. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
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If the fuel pressure drops, locate and replace the leaking fuel injector.
7. If the fuel system test normal, replace the fuel pump.
2. Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 minutes.
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If the fuel pressure decreases more than the specified value, replace the fuel pump.
3. Remove the J 37287 and CH-48027.
4. Operate the vehicle within the conditions of the customers concern while monitoring the fuel trim and O2 parameters with a scan tool. The scan
tool parameters should not indicate a lean condition.
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If the scan tool parameters indicate a lean condition, test for a restricted fuel feed pipe, restricted fuel filter, or poor connections at the harness
connectors and ground circuits of the fuel pump. If all test normal, replace the fuel pump.
5. If the fuel system components test normal, refer to Symptoms - Computers and Control Systems. See: Computers and Control Systems/Testing
and Inspection/Symptom Related Diagnostic Procedures/Symptoms - Engine Controls
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. See: Computers and Control Systems/Testing and
Inspection/Diagnostic Trouble Code Tests and Associated Procedures/Verification Tests and Procedures
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Fuel Injector Replacement
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Fuel Tank Fuel Pump Module Replacement (1500 Series) Fuel Tank Fuel Pump Module Replacement (1500 SWB - 98.4L (26 gal) Tank + E85)
Fuel Tank Fuel Pump Module Replacement (1500 LWB - 117.3L (31 gal) Tank + E85) Fuel Tank Fuel Pump Module Replacement (2500 LWB -
98.4L (26 gal) Tank-Front) Fuel Tank Fuel Pump Module Replacement (2500 LWB - 43.5L (11.5 gal) Tank-Rear)
Fuel System Diagnosis (W/FPCM)
Fuel System Diagnosis (w/FPCM)
Diagnostic Instructions
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Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and
Diagnostic Overview/Diagnostic System Check - Vehicle
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Review Strategy Based Diagnosis for an overview of the diagnostic approach.
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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.
The fuel system is a returnless on-demand design. The fuel pressure regulator is a part of the fuel pump module, eliminating the need for a return pipe
from the engine. A returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank.
