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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Headlight Switch 12V Reference
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1
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1
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1
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-
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Headlight Switch Signal
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1
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1
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2
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-
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Rear Fog Lamps Control
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B2540 02
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B2540 04
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1
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-
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1. Rear fog lamps inoperative
2. Rear fog lamps always On
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Circuit/System Description
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The rear fog lamp switch signal circuit is grounded momentarily by pressing the rear fog lamp switch. The body control module (BCM) energizes the rear fog lamp supply voltage circuit which illuminates the rear fog lamp. With the rear fog lamp switch activated the BCM sends a message via serial data to the instrument cluster requesting the instrument cluster to illuminate the rear fog indicator.
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 information on diagnostic tools
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Circuit/System Verification
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Ignition ON, perform the scan tool Rear Fog Lamps Switch parameter. The reading should change between Active/Inactive when changing between pressed and released rear fog lamp switch button.
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If no change between Active and Inactive, refer to Rear Fog Lamp Switch Malfunction.
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Ignition ON, perform the instrument cluster All Indicators test ON and OFF test. The rear fog indicator should be ON/OFF.
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If no change between ON and OFF, refer to Rear Fog Indicator Malfunction.
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Ignition ON, perform the Rear Fog Lamp(s) Relay test. The rear fog lamp should be ON/OFF when changing between the commanded states.
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If no change between ON and 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 X1 and X3 harness connector at the K9 Body Control Module.
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2.
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Test for less than 0.3 V between the 12 V reference circuit terminal 4 X3 and ground.
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3.
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If greater than the specified value, test the 12 V Reference circuit for an short to voltage.
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4.
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Test for less than 0.3 V between the signal circuit terminal 9 X1 and ground.
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5.
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If greater then the specified value, test the signal circuit for a short to voltage.
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6.
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Test for infinite resistance between the signal circuit terminal 9 X1 and ground.
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7.
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If less than the specified value, test the signal circuit for a short to ground.
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8.
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Test for infinite resistance between the 12 V reference circuit terminal 4 X3 and ground.
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9.
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If less than the specified value, test the 12 V reference circuit for an short to ground.
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10.
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Press and hold the rear fog lamp switch button.
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11.
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Test for 2.0-2.4 kΩ between the signal circuit terminal 9 X1 and the 12 V reference circuit terminal 4 X3.
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12.
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If not within the specified range, test the 12 V reference circuit and the signal circuit for an open/high resistance. If the circuit test normal, replace the S30 Headlamp Switch.
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13.
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If all circuit test normal, replace the K9 Body Control Module.
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Rear Fog Indicator Malfunction
Ignition ON, command the instrument cluster All Indicators test ON and OFF with the scan tool. The rear fog indicator lamp should be ON/OFF when changing between the commanded states.
If the rear fog indicator stays always on or always off, replace the P16 Instrument Cluster.
If the rear fog indicator is changing between ON and OFF, replace the K9 Body Control Module.
Rear fog lamp malfunction
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1.
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Ignition OFF, disconnect the harness connector at the E29R Fog Lamp - Rear.
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2.
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Test for less than 5 Ω between the ground circuit terminal A 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 harness connector terminal B and ground.
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5.
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Ignition ON, perform the Rear Fog Lamps Relay Command test. The test lamp must be ON/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 Body Control Module.
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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 circuits test normal, replace the K9 Body Control Module.
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8.
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If all circuits test normal, replace the E29R Fog Lamp - Rear.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
