Home ReviewsRefund
Home/Cadillac/STS/Cadillac STS I (2004-2007)/Repair manual/Exterior Lights/Lighting Systems (Symptoms): Diagnosis
Contents Wiring diagrams Section: Exterior Lights All sections

Lighting Systems (Symptoms): Diagnosis Cadillac STS I

Exterior Lights ~397 words

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the lighting system. Refer to «Checking Aftermarket Accessories»(ref-197533-S03944243902005101200000) in Wiring Systems.
  2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

  1. «Backup Lamps Always On»(ref-197549-S00216400212005101200000)
  2. «Backup Lamps Inoperative»(ref-197549-S41919894572005101200000)
  3. «Cornering Lamps Inoperative»(ref-197549-S36613796512005101200000)
  4. «Courtesy Lamps Always On»(ref-197549-S26385059182005101200000)
  5. «Courtesy Lamps Inoperative»(ref-197549-S38243866582005101200000)
  6. «Daytime Running Lamps (DRL) Inoperative (Domestic/Canadian)»(ref-197549-S40103259372005101200000) or «Daytime Running Lamps (DRL) Inoperative (Norway/Sweden)»(ref-197549-S06524006712005101200000)
  7. «Fog Lamp Indicator Always On»(ref-197549-S16124218642005101200000)
  8. «Fog Lamp Indicator Inoperative»(ref-197549-S27644022512005101200000)
  9. «Fog Lamp Indicator Always On - Rear (Export)»(ref-197549-S04197589362005101200000)
  10. «Fog Lamp Indicator Inoperative - Rear (Export)»(ref-197549-S26046079712005101200000)
  11. «Fog Lamps Always On»(ref-197549-S40146943132005101200000)
  12. «Fog Lamps Inoperative»(ref-197549-S22601181712005101200000)
  13. «Fog Lamps Always On - Rear»(ref-197549-S03938688922005101200000)
  14. «Fog Lamps Inoperative - Rear»(ref-197549-S15461201722005101200000)
  15. «Hazard Lamps Always On»(ref-197549-S37742858672005101200000)
  16. «Hazard Lamps Inoperative»(ref-197549-S12576500742005101200000)
  17. «Headlamps Always On - Low or High Beam (Standard)»(ref-197549-S20452843462005101200000) or «Headlamps Always On - Low or High Beam (with Intellibeam)»(ref-197549-S07721453632005101200000)
  18. «Headlamps Inoperative - High Beams (Standard)»(ref-197549-S19877401092005101200000) or «Headlamps Inoperative - High Beams (with Intellibeam)»(ref-197549-S42830797372005101200000)
  19. «Headlamps Inoperative - Low Beams (Standard Headlamps)»(ref-197549-S24760780492005101200000) or «Headlamps Inoperative - Low Beams (HID Headlamps)»(ref-197549-S02004745982005101200000)
  20. «Headlamps Inoperative - Flash to Pass»(ref-197549-S02130093462005101200000)
  21. «High Beam Indicator Always On»(ref-197549-S08367536312005101200000)
  22. «High Beam Indicator Inoperative (Standard)»(ref-197549-S16599995982005101200000) or «High Beam Indicator Inoperative (with Intellibeam)»(ref-197549-S07230074412005101200000)
  23. «Illuminated Entry Lamps Inoperative»(ref-197549-S41684016602005101200000)
  24. «Interior Backlighting Does Not Dim»(ref-197549-S14072010222005101200000)
  25. «Interior Backlighting Inoperative»(ref-197549-S37598290452005101200000)
  26. «Instrument Panel (I/P) Compartment Lamp Inoperative»(ref-197549-S39575671132005101200000)
  27. «License Lamps Inoperative»(ref-197549-S11428947142005101200000)
  28. «Lights On Indicator Always On»(ref-197549-S29444657922005101200000)
  29. «Lights On Indicator Inoperative»(ref-197549-S33014310482005101200000)
  30. «Park Lamps Always On»(ref-197549-S32322991372005101200000)
  31. «Park Lamps Inoperative»(ref-197549-S10679821342005101200000)
  32. «Reading Lamp(s) Inoperative»(ref-197549-S07522085712005101200000)
  33. «Rear Compartment Lamp(s) Always On»(ref-197549-S12705826052005101200000)
  34. «Rear Compartment Lamp(s) Inoperative»(ref-197549-S35736240692005101200000)
  35. «Repeater Lamps Inoperative»(ref-197549-S21080496992005101200000)
  36. «Stop Lamps Always On»(ref-197549-S23303385062005101200000)
  37. «Stop Lamps Inoperative»(ref-197549-S26857722582005101200000)
  38. «Turn Signal Lamps and/or Indicators Always On or Flashing»(ref-197549-S06645580222005101200000)
  39. «Turn Signal Lamps and/or Indicators Inoperative»(ref-197549-S40717154322005101200000)
  40. «Twilight Sentinel Inoperative»(ref-197549-S06914727742005101200000)
  41. «Vanity Mirror Lamp(s) Always On»(ref-197549-S42430363662005101200000)
  42. «Vanity Mirror Lamp(s) Inoperative»(ref-197549-S14807342792005101200000)

Diagnostic Aids

IMPORTANTThe stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation .

Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

StepActionYesNo
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2Turn OFF the ignition. Disconnect the stop lamp relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Turn ON the ignition, with the engine OFF. Do the stop lamps turn OFF?Go to Step 3Go to Step 7
3Turn OFF the ignition. Connect a test lamp between the stop lamp switch signal circuit at the coil side of the stop lamp relay and the stop lamp voltage supply circuit at the switch side of the stop lamp relay. Turn ON the ignition, with the engine OFF. Press and release the brake pedal. Does the test lamp turn ON and OFF?Go to Step 5Go to Step 4
4Test the stop lamp switch signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 10Go to Step 6
5Inspect for poor connections at the stop lamp relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 10Go to Step 8
6Inspect for poor connections at the harness connector of the instrument panel module (IPM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 10Go to Step 9
7Test the stop lamp voltage supply circuit between the tail lamp assembly and the fuse block-right rear for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 10
8Replace the stop lamp relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the replacement?Go to Step 10
9Replace the IPM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?Go to Step 10
10Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2

Stop Lamps Always On

IMPORTANTThe stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation .

Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

StepActionYesNo
Schematic Reference: Exterior Lights Schematics Connector End View Reference: Master Electrical Component List in Wiring Systems
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2Are all of the stop lamps inoperative?Go to Step 3Go to Step 5
3Turn OFF the ignition. Disconnect the stop lamp relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Connect a test lamp between the stop lamp switch signal circuit at the coil side of the stop lamp relay and ground. Turn ON the ignition, with the engine OFF. Press and release the brake pedal. Does the test lamp illuminate?Go to Step 4Go to Step 9
4Turn OFF the ignition. Connect a 10-amp fused jumper between the stop lamp relay switch side supply voltage and the stop lamp voltage supply circuit at the switch side of the stop lamp relay. Turn ON the ignition, with the engine OFF. Do the stop lamps illuminate?Go to Step 8Go to Step 5
5Test the voltage supply circuit of the inoperative stop lamp for the following: An open A high resistance A short to ground Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 14Go to Step 6
6Test the ground circuit of the inoperative stop lamp for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 14Go to Step 7
7Inspect for poor connections at the harness connector of the inoperative stop lamp or center high mounted stop lamp (CHMSL). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 14Go to Step 13
8Inspect for poor connections at the stop lamp relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 14Go to Step 12
9Test the stop lamp switch signal circuit for the following: An open A high resistance A short to ground Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 14Go to Step 10
10Inspect for poor connections at the harness connector of the instrument panel module (IPM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?Go to Step 14Go to Step 11
11Replace the IPM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?Go to Step 14
12Replace the stop lamp relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Did you complete the replacement?Go to Step 14
13Replace the inoperable stop lamp. Refer to Tail Lamp, Turn Signal Lamp, High Mount Stop Lamp, License Lamp, Backup Lamp Replacement - Rear . Did you complete the replacement?Go to Step 14
14Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2

Stop Lamps Inoperative

More articles — Lighting Systems (Symptoms)