Trailer Lamps Malfunction (With U4G)
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Trailer Lamps Malfunction (With U4G)
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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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Trailer Brake Control Module B+
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B1325 03
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B1325 03
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-
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-
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Center High Mounted Stop Lamp Signal
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5
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5
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5
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B0655 5A
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Backup Lamps Control
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B3890 02
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B3890 04
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2
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-
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Stop Lamps Control
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B3889 02
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B3889 04
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5
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-
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Left Turn Signal Lamps Control
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B3887 02
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B3887 04
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6
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-
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Right Turn Signal Lamps Control
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B3888 02
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B3888 04
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7
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-
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Trailer Fog Lamp Control
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B3891 02
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B3891 04
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3
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-
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Trailer Left Park Lamp Control
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B3885 02
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B3885 04
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4
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-
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Trailer Right Park Lamp Control
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B3886 02
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B3886 04
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4
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-
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Trailer Brake Control Module Ground
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-
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1
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-
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-
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Trailer Connector Ground
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-
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1
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-
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-
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1. All Trailer Lamps Inoperative
2. Trailer Backup Lamps Malfunction
3. Trailer Fog Lamps Malfunction
4. Trailer Park/Tail Lamps Malfunction
5. Trailer Brake Lamps Malfunction
6. Trailer Left Turn Signal Lamp Malfunction
7. Trailer Right Turn Signal Lamp Malfunction
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Circuit/System Description
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The trailer brake control module will receive a serial data message from the BCM indicating when each of the vehicle exterior lights have been activated. The trailer brake control module will then apply voltage to the appropriate trailer lamps through their respective voltage supply circuits.
Schematic Reference
Trailer Connector/Provision 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 function of the left trailer tail lamp and the right trailer tail lamp while commanding the Left Trailer Tail Lamp and the Right Trailer Tail Lamp ON and OFF with a scan tool. The left trailer tail lamp and the right trailer tail lamp should turn ON and OFF while changing between the commanded states.
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2.
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If the left trailer tail lamp or the right trailer tail lamp is always ON or always OFF, refer to Trailer Lamps Malfunction.
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3.
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Observe the function of the left trailer turn signal lamp and the right trailer turn signal lamp while commanding the Left Trailer Turn Signal Lamp and the Right Trailer Turn Signal Lamp ON and OFF with a scan tool. The left trailer turn signal lamp and the right trailer turn signal lamp should turn ON and OFF while changing between the commanded states.
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4.
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If the left trailer turn signal lamp or the right trailer turn signal lamp is always ON or always OFF, refer to Trailer Lamps Malfunction.
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5.
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Observe the function of the trailer fog lamps while commanding the Trailer Fog Lamps ON and OFF with a scan tool. The trailer fog lamps should turn ON and OFF while changing between the commanded states.
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6.
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If the trailer fog lamps are always ON or always OFF, refer to Trailer Lamps Malfunction.
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7.
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Observe the function of the trailer backup lamps while commanding the Trailer Backup Lamps ON and OFF with a scan tool. The trailer backup lamps should turn ON and OFF while changing between the commanded states.
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8.
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If the trailer backup lamps are always ON or always OFF, refer to Trailer Lamps Malfunction
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9.
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Observe the function of the trailer brake lamps while commanding the Trailer Brake Lamps ON and OFF with a scan tool. The trailer stop lamps should turn ON and OFF while changing between the commanded states.
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10.
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If the trailer brake lamps are always ON or always OFF, refer to Trailer Brake Lamps Malfunction.
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11.
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If all trailer lamps are inoperative, refer to All Trailer Lamps Inoperative.
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Trailer Lamps Malfunction
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1.
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Note
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Verify that the trailer has been disconnected from the X88 trailer connector.
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Ignition OFF, disconnect the X1 harness connector at the K67 trailer brake control module.
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2.
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Test for infinite resistance between the control circuit terminal listed below and ground:
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•
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Right trailer turn signal lamp control terminal 2
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•
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Left trailer park lamp control terminal 4
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•
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Trailer backup lamp control terminal 7
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•
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Trailer fog lamp control terminal 8
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•
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Right trailer park lamp control terminal 16
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•
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Left trailer turn signal lamp control terminal 17
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3.
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If not the specified value, test the control circuit for a short to ground. If the circuit tests normal, replace the X88 trailer connector.
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4.
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Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal listed below and ground:
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Right trailer turn signal lamp control terminal 2
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•
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Left trailer park lamp control terminal 4
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•
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Trailer backup lamp control terminal 7
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•
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Trailer fog lamp control terminal 8
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•
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Right trailer park lamp control terminal 16
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Left trailer turn signal lamp control terminal 17
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5.
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If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the X88 trailer connector.
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6.
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Test for less than 1 Ω between the control circuit terminals listed below:
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Right trailer turn signal lamp control terminal 2 at the K67 trailer brake control module and control terminal 4 at the X88 trailer connector.
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Left trailer park lamp control terminal 4 at the K67 trailer brake control module and control terminal 7 at the X88 trailer connector.
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Trailer backup lamp control terminal 7 at the K67 trailer brake control module and control terminal 8 at the X88 trailer connector.
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Trailer fog lamp control terminal 8 at the K67 trailer brake control module and control terminal 2 at the X88 trailer connector.
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Right trailer park lamp control terminal 16 at the K67 trailer brake control module and control terminal 5 at the X88 trailer connector.
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Left trailer turn signal lamp control terminal 17 at the K67 trailer brake control module and control terminal 1 at the X88 trailer connector.
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7.
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If greater than the specified range, test the control circuit for an open/high resistance. If the circuit tests normal, replace the X88 trailer connector.
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8.
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If all circuits test normal, replace the K67 trailer brake control module.
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Trailer Brake Lamps Malfunction
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1.
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Ignition OFF, disconnect the X1 harness connector at the K67 trailer brake control module.
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2.
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Connect a test lamp between the signal circuit terminal 14 and ground.
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3.
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Ignition ON, command the Center Brake Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF while changing between the commanded states.
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4.
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If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, refer to
Stop Lamps Malfunction
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5.
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If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, refer to
Stop Lamps Malfunction
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6.
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Verify that a test lamp does not illuminate between the control circuit terminal 10 and ground.
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7.
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If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the X88 trailer connector.
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8.
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Test for infinite resistance between the control circuit terminal 10 and ground.
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9.
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If not the specified value, test the control circuit for a short to ground. If the circuit tests normal, replace the X88 trailer connector.
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10.
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Test for less than 1 Ω between the control circuit 10 at the K67 trailer brake control module and the control circuit terminal 6 at the X88 trailer connector.
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11.
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If greater than the specified range, test the control circuit for an open/high resistance. If the circuit tests normal, replace the X88 trailer connector.
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12.
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If all circuits test normal, replace the K67 trailer brake control module.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
Control Module References
for trailer brake control module replacement, programming and setup
