A Preliminary Information

IMPORTANT: The following steps must be completed before using the symptom tables.
1. Perform A Diagnostic System Check - Lighting Systems before using the Symptom Tables in order to verify that all of the following are true:
- There are no DTCs set.
- The control module(s) can communicate via the serial data link.
2. Review the system operation and circuit descriptions that apply to the customer complaint in order to familiarize yourself with the system functions. Refer to the following list:
- Headlights Circuit Description
- Headlights/Daytime Running Lights (DRL) Circuit Description
- Fog Lights Circuit Description
- Headlight Leveling Circuit Description
- Exterior Lights Circuit Description
- Backup Lights Circuit Description
- Interior Lights Circuit Description
- Interior Lights Dimming Circuit Description

VISUAL/PHYSICAL INSPECTION
- Inspect for aftermarket devices which could affect the operation of the lighting system. Refer to Checking Aftermarket Accessories in Diagrams.
- Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

INTERMITTENT
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent and Poor Connections in Diagrams.

SYMPTOM LIST
Refer to a Symptom Diagnostic Procedure from the following list in order to diagnose the symptom:
- Backup Lamps Always On
- Backup Lamps Inoperative (Pickup) or Backup Lamps Inoperative (Utility)
- Backup Lamp Inoperative - One Lamp (Pickup) or Backup Lamp Inoperative - One Lamp (Utility)
- Component Illumination Lamps Inoperative
- Courtesy or Dome Lamps Always On
- Courtesy or Dome Lamps Inoperative
- Daytime Running Lamps (DRL) Headlamps Always On (Standard) or Daytime Running Lamps (DRL) Headlamps Always On (Envoy/Diamond Edition 1SK) or Daytime Running Lamps (DRL) Headlamps Always On (ZR2)
- Daytime Running Lamps (DRL) Headlamps Inoperative (Standard) or Daytime Running Lamps (DRL) Headlamps Inoperative (Envoy/Diamond Edition 1SK) or Daytime Running Lamps (DRL) Headlamps Inoperative (ZR2)
- Fog Lamp Indicator Inoperative
- Fog Lamps Always On
- Fog Lamps Inoperative - All
- Fog Lamps Inoperative - Rear
- Hazard Lamps Inoperative
- Headlamps Inoperative - Left Low Beam (Standard) or Headlamps Inoperative - Left Low Beam (Envoy/Diamond Edition 1SK)
- Headlamps Inoperative - Right Low Beam (Standard) or Headlamps Inoperative - Right Low Beam (Envoy/Diamond Edition 1SK)
- Headlamps Inoperative - Low Beams
- Headlamps Inoperative - Left High Beam (Standard) or Headlamps Inoperative - Left High Beam (Envoy/Diamond Edition 1SK)
- Headlamps Inoperative - Right High Beam (Standard) or Headlamps Inoperative - Right High Beam (Envoy/Diamond Edition 1SK)
- Headlamps Inoperative - High Beams (Standard) or Headlamps Inoperative - High Beams (Envoy/Diamond Edition 1SK)
- Headlamps Inoperative In Low Light Conditions
- Headlight Leveling Inoperative
- High Beam Indicator Always On
- High Beam Indicator Inoperative
- Instrument Cluster Illumination Lamps Always On
- Instrument Cluster Illumination Lamps Do Not Dim
- Instrument Cluster Illumination Lamps Inoperative
- IP Compartment Lamp Inoperative
- Vanity Mirror Lamp(s) Inoperative
- Underhood Lamp Inoperative
- Instrument Panel Lamps Inoperative
- Park Lamps Inoperative - Front
- Park Lamps Inoperative in Low Light Conditions
- Park, Tall and Side Marker Lamps Inoperative
- Rearview Mirror Lamp(s) Inoperative - Inside
- Marker, License and Tall Lamps Inoperative
- Stop Lamps Inoperative (Pickup/Utility Except Export) or Stop Lamps Inoperative (Export)
- Stop Lamps Inoperative - One (Pickup) or Stop Lamps Inoperative - One (Utility) or Stop Lamps Inoperative - One (Export)
- Stop Lamps Inoperative - Center High Mounted
- Tall Lamps Inoperative - LR
- Tall Lamps Inoperative - RR
- Turn Signal Lamps Inoperative
- [1][2]Turn Signal Lamp Inoperative - LF
- [1][2]Turn Signal Lamp Inoperative - RF
- Turn Signal Lamps Inoperative - LR
- [1][2]Turn Signal Lamp Inoperative - RR
- Turn Signal Indicator Always On - Left
- Turn Signal Indicator Always On - Right
- Turn Signal Indicators Inoperative - Left
- Turn Signal Indicators Inoperative - Right