Rear Fog Lamps Malfunction
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Rear Fog Lamps Malfunction
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Diagnostic Fault Information
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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Headlamp Switch Reference Voltage
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B257B 03
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B257B 03
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-
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B3588 00
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Headlight Switch Signal
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B257B 03
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B257B 03
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B257B 07
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-
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Rear Fog Lamps Control
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B2540 02
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2
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1
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-
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Tail Lamp Ground
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-
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2
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-
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-
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1. Rear fog lamp always ON
2. Rear fog lamp always OFF
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Circuit/System Description
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The body control module (BCM) supplies a reference voltage to the backlight dimmer switch, which is part of the headlamp switch. When the backlight dimmer switch is placed in a desired brightness position, reference voltage is applied through the backlight dimmer switch resistor ladder to the BCM. The BCM interprets this voltage signal and will command the interior lights to the desired brightness, command the front fog lamps or the rear fog lamps depending upon the switch setting selected.
Schematic Reference
Fog Lights Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Exterior Lighting Systems Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References
for scan tool information
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Circuit/System Verification
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1.
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Ignition ON, observe the scan tool Rear Fog Lamps Switch parameter. The parameter should change between Active and Inactive each time the rear fog lamp switch is pressed.
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2.
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If the value does not change, refer to Rear Fog Lamp Switch Malfunction
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3.
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Command the Rear Fog Lamp(s) Relay ON and OFF with a scan tool. The rear fog lamp should turn ON and OFF when changing between the commanded states
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4.
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If the rear fog lamps are always ON or always OFF, refer to Rear Fog Lamp Malfunction
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Rear Fog Lamp Switch Malfunction
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1.
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Ignition OFF, disconnect the harness connector at the S30 headlamp switch.
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2.
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Ignition OFF, test for 0.4K Ω to 1 Ω between the signal circuit terminal 12 and ground.
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3.
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If greater than the specified value, test the low reference circuit for an short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
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4.
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If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the K9 BCM.
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5.
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Test for greater than 10 V between the 12 V reference circuit terminal 1 and ground.
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6.
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If less than the specified range, test the 12V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
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7.
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If all circuits test normal, replace the K9 BCM.
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Rear Fog Lamp Malfunction
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1.
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Ignition OFF, disconnect the harness connector at the E5 fog lamp-rear.
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2.
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Test for less than 30 Ω between the ground circuit terminal C and ground.
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3.
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If greater than the specified range, test the ground circuit for an open/high resistance.
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4.
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Connect a test lamp between the control circuit terminal A and ground.
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5.
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Ignition ON, command the Rear Fog Lamp(s) Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
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6.
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If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
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7.
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If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
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8.
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If all circuits test normal, replace the E5 fog lamp-rear.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
