F 250 2WD Super Duty V8-5.4L (2008)
Daytime Running Lamp: Initial Inspection and Diagnostic Overview
Inspection and Verification
INSPECTION AND VERIFICATION
1. Verify the customer concern.
2. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
NOTE:
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Make sure the headlamp switch is in the OFF position.
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Make sure the multifunction switch is not in the HIGH BEAM position.
3. NOTE: Make sure to use the latest scan tool software release.
If the cause is not visually evident, connect the scan tool to the data link connector (DLC).
4. NOTE: The vehicle communication module (VCM) LED prove-out confirms power and ground from the DLC are provided to the VCM.
If the scan tool does not communicate with the VCM:
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Check the VCM connection to the vehicle.
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Check the scan tool connection to the VCM.
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Refer to Information Bus (Module Communications Network), No Power To The Scan Tool, to diagnose no communication with the scan tool.
5. If the scan tool does not communicate with the vehicle:
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Verify the ignition key is in the ON position.
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Verify the scan tool operation with a known good vehicle.
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Refer to Information Bus (Module Communications Network) to diagnose no response from the PCM.
6. Carry out the network test.
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If the scan tool responds with no communication for one or more modules, refer to Information Bus (Module Communications Network).
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If the network test passes, retrieve and record the continuous memory DTCs.
7. Check the smart junction box (SJB) and make sure the daytime running lamps (DRL) configuration is enabled.
8. Check the operation of the brake warning indicator by applying and releasing the parking brake.
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If the brake warning indicator does not operate correctly, refer to Instrumental panel, Gauges and Warnings Indicators.
9. Check the operation of the PRNDL display by placing the gear selector lever in each of its positions.
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If the PRNDL display does not operate correctly, refer to Instrumental panel, Gauges and Warnings Indicators.
10. If no DTCs related to the concern are retrieved, GO to Symptom Chart. See: Symptom Related Diagnostic Procedures
Principles of Operation
PRINCIPLES OF OPERATION
NOTE:
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The smart junction box (SJB) is also known as the generic electronic module (GEM).
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When installing a new SJB, it must be configured for this feature, if originally equipped. Refer to Information Bus (Module Communications
Network).
The SJB controls the DRL by using various inputs to determine whether or not the DRL should be illuminated. These inputs include:
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Ignition switch position
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Headlamp switch position
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Headlamps on or off
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Transmission gear selection (automatic transmission)
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Parking brake applied or released (manual transmission)
When the DRL is active, the SJB provides a pulse-width modulated (PWM) voltage to the low beam headlamps. This illuminates the headlamps at a
reduced intensity.
