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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 STS 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Headlamp Low or High Beams Always On

Headlamp Low or High Beams Always On Standard

Step

Action

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics and Wiper/Washer Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Turn the headlamp switch to the OFF position.
  4. With a scan tool, observe the Headlamp Switch parameter in the instrument panel module (IPM) inputs data list.

Does the scan tool indicate the Headlamp Switch parameter is OFF?

Go to Step 3

Go to Step 12

3

With a scan tool, observe both the Low Beam and High Beam Relay parameters in the IPM outputs data list.

Does the scan tool indicate the Low Beam and High Beam Relay output parameters are OFF?

Go to Step 7

Go to Step 4

4

With a scan tool, observe the Lights On With Wipers parameter in the IPM inputs data list.

Does the scan tool indicate OFF?

Go to Step 5

Go to Step 13

5

With the scan tool, observe the Flash to Pass Switch parameter in the IPM inputs data list.

Does the scan tool indicate that the Flash to Pass Switch parameter is INACTIVE?

Go to Step 6

Go to Step 14

6

With a scan tool, observe the Twilight Enable status in the IPM exterior lamps data list.

Does the scan tool indicate that the Twilight Enable is DISABLED?

Go to Step 22

Go to Twilight Sentinel Inoperative

7

Are the high beam headlamps ON?

Go to Step 10

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Disconnect the headlamp low beam relay.
  3. Turn ON the ignition, with the engine OFF.

Do the low beam headlamps turn OFF?

Go to Step 9

Go to Step 23

9
  1. Turn OFF the ignition.
  2. Turn OFF the headlamp switch.
  3. Connect a test lamp between the low beam relay coil side supply voltage circuit and the headlamp low beam relay control circuit.
  4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

Go to Step 15

Go to Step 19

10
  1. Turn OFF the ignition.
  2. Disconnect the headlamp high beam relay.
  3. Turn ON the ignition, with the engine OFF.

Do the high beam headlamps turn OFF?

Go to Step 11

Go to Step 24

11
  1. Turn OFF the ignition.
  2. Turn OFF the headlamp switch.
  3. Connect a test lamp between the coil side supply voltage circuit of the headlamp high beam relay and the headlamp high beam relay control circuit.
  4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

Go to Step 16

Go to Step 20

12
  1. Turn OFF the ignition.
  2. Disconnect the turn signal/multifunction switch.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Head Lamp Switch parameter in the IPM inputs data list.

Does the scan tool indicate that the Head Lamp Switch parameter is OFF?

Go to Step 21

Go to Step 17

13

Test the windshield wiper switch ON signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 22

14
  1. Turn OFF the ignition.
  2. Disconnect the turn signal/multifunction switch.
  3. With a scan tool, observe the Flash to Pass Switch parameter in the IPM inputs data list.

Does the scan tool indicate that the Flash to Pass Switch is INACTIVE?

Go to Step 21

Go to Step 18

15

Locate and repair a short to ground in the headlamp low beam relay control circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 22

16

Locate and repair a short to ground in the headlamp high beam relay control circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 22

17

Locate and repair a short to ground in the headlamp switch headlamp ON signal circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 22

18

Test the flash to pass switch signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 22

19

Inspect for poor connections at the low beam relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 25

20

Inspect for poor connections at the high beam relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 26

21

Inspect for poor connections at the harness connector of the turn signal/multifunction switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 27

22

Inspect for poor connections at the harness connector of the IPM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 28

23

Locate and repair a short to voltage in the headlamp low beam supply voltage circuit. Refer to Circuit Testing and Wiring Repairs .

Did you complete the repair?

Go to Step 29

--

24

Locate and repair a short to voltage in the headlamp high beam supply voltage circuit. Refer to Circuit Testing and Wiring Repairs .

Did you complete the repair?

Go to Step 29

--

25

Replace the headlamp low beam relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 29

--

26

Replace the headlamp high beam relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 29

--

27

Replace the turn signal/multifunction switch. Refer to Turn Signal Multifunction Switch Replacement .

Did you complete the replacement?

Go to Step 29

--

28

Replace the IPM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 29

--

29

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2

Headlamp Low or High Beams Always On with Intellibeam

Step

Action

Yes

No

Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics and Inside Rearview Mirror Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn OFF the ignition.
  2. Disconnect the inside rearview mirror (ISRVM) harness connector. Refer to Inside Rearview Mirror Replacement .
  3. Turn ON the ignition, with the engine OFF.

Do the high beam headlamps turn OFF?

Go to Step 3

Go to Step 5

3
  1. Turn OFF the ignition.
  2. Connect a test lamp between the headlamp high beam relay control circuit and battery voltage at the ISRVM harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Place the headlamp switch in the low beam position.

Does the test lamp illuminate?

Go to Step 4

Go to Step 7

4

Locate and repair a short to ground in the headlamp high beam relay control circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 14

Go to Step 9

5
  1. Turn OFF the ignition.
  2. Disconnect the automatic headlamp dimming relay.
  3. Turn ON the ignition, with the engine OFF.

Do the high beam headlamps turn OFF?

Go to Step 6

Go to Step 10

6

Test the automatic high beam PWM signal circuit for a short. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 14

Go to Step 8

7

Inspect for poor connections at the harness connector of the ISRVM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 14

Go to Step 11

8

Inspect for poor connections at the harness connector of the automatic headlamp dimming relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 14

Go to Step 12

9

Inspect 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 .

Did you find and correct the condition?

Go to Step 14

Go to Step 13

10

Locate and repair a short to battery voltage in the headlamp high beam voltage supply circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 14

--

11

Replace the ISRVM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 14

--

12

Replace the automatic headlamp dimming relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 14

--

13

Replace the IPM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 14

--

14

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2