Sierra 2500 2WD V8-6.6L DSL Turbo (2007)
Fuel Heater: Testing and Inspection
Fuel Heater Always On
Fuel Heater Always On
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 fuel filter/heater element housing consists of a water separator, a hand prime pump, fuel heater element and a filter element. Fuel passes through the
fuel heater, which is operated by a built-in thermostatic switch. The thermostatic switch opens or closes to turn the heater ON or OFF, depending on
temperature. Fuel then passes through the filter and the water coalescer, where the droplets of water in the fuel combine into larger drops that fall into the
water reservoir in the filter. When fuel flows to the fuel injection pump, the fuel is clean and free of water.
Circuit/System Testing
Check the Water in Fuel lamp for proper operation. Refer to Water-in-Fuel Lamp Always On. See: Instrument Panel, Gauges and Warning
Indicators/Testing and Inspection/Symptom Related Diagnostic Procedures/Water-in-Fuel Lamp Always On
1. Turn ON the ignition, with the engine OFF.
2. Disconnect the fuel heater connector.
3. With the fuel temperature above 21°C (70°F), test for continuity between the ignition 1 voltage terminal and the fuel filter/heater element housing.
‹› If continuity was present, the thermostatic switch is stuck ON. Replace the fuel filter/heater element housing.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. See: Testing and Inspection/Initial Inspection and Diagnostic
Overview/Diagnostic System Check - Vehicle
Fuel Filter Assembly Replacement
