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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2005 🢒 XLR 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 High Mount Stop Lamp Always On

Diagnostic Aids

Important: The 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.

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Turn ON the ignition, with the engine OFF.
  2. Depress and hold the brake pedal.
  3. Observe the high mounted stop lamp (HMSL).
  4. Release the brake pedal.

Did the HMSL operate properly?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Are DTCs P0719 or P0724 set as current?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Disconnect the stop lamp relay. Refer to Relay Replacement in Wiring Systems.
  3. Turn ON the ignition, with the engine OFF.

Does the HMSL turn OFF?

Go to Step 5

Go to Step 8

5
  1. Turn OFF the ignition.
  2. Connect a test lamp between the stop lamp relay control side supply voltage circuit and the stop lamp relay control circuit.
  3. Turn ON the ignition, with the engine OFF.
  4. Apply and unapply the brake pedal several times.

Does the test lamp turn ON and OFF when the brake pedal is applied and unapplied?

Go to Step 6

Go to Step 7

6

Inspect 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 11

Go to Step 9

7

Inspect for poor connections at the harness connector of the body control module (BCM). 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 11

Go to Step 10

8

Locate and repair a short to voltage in the HMSL supply voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

--

9

Replace the stop lamp relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 11

--

10

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 11

--

11

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2