GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Sonoma Pickup - 4WD 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Stop Lamps Always On

Step

Action

Yes

No

Schematic Reference: Exterior Lights Schematics

1

Did you review the Exterior Lighting Systems Description and Operation and perform the necessary inspections?

Go to Step 2

Go to Exterior Lighting Systems Description and Operation

2

Verify that the stop lamps are always on.

Do the stop lamps operate normally?

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

Go to Step 3

3

Disconnect the stop lamp switch.

Do the stop lamps remain illuminated?

Go to Step 4

Go to Step 7

4

Disconnect the multifunction turn signal switch and the high mount stop lamp (CHMSL) relay (pickup only) and test for a short to voltage in the following circuits. Refer to Circuit Testing in Wiring Systems:

    • CHMSL supply voltage
    • Stop lamp switch signal
    • Left rear stop lamp supply voltage (pickup only)

Was a problem found?

Go to Step 6

Go to Step 5

5
  1. Test the CHMSL relay (pickup only) for shorted internal contacts and replace as necessary.
  2. If the vehicle is not equipped with CHMSL relay or a relay fault is not found, replace the multifunction switch turn signal switch. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle Steering Wheel and Column.

Did you complete the repair?

Go to Step 8

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6

Repair the short to voltage in one of the following circuits. Refer to Wiring Repairs in Wiring Systems:

    • CHMSL Supply Voltage
    • Stop lamp switch signal
    • Left rear stop lamp supply voltage (pickup only)

Did you complete the repair?

Go to Step 8

--

7

Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.

Did you complete the repair?

Go to Step 8

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8

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3