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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1479 (ANTILOCK BRAKE SYSTEM, TRACTION CONTROL SYSTEM & STABILITY CONTROL SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC C1291TEST DESCRIPTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Test Description

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Description
WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 3:  Tests the circuit for a change in states.
  2. 5:  Tests for proper operation of the circuit by bypassing the stoplamp switch. If the fuse in the jumper opens when you perform this test, the signal circuit of the stop lamp switch is shorted to ground.
DTC C1291

Step Action Yes No
Schematic Reference:  ABS Schematics  
Connector End View Reference:  ABS Connector End Views  
1 Did you perform the ABS Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - ABS 
2 Press the brake pedal.
Do the brake lamps turn ON?		 Go to Step 3  Go to Step 7 
3 
  1. Press the brake pedal.
  2. With a scan tool, observe the Stop Lamp Switch parameter in the TCS data list.
Does the Stop Lamp Switch parameter change state?		 Go to Diagnostic Aids Go to Step 4 
4
  1. Turn OFF the ignition.
  2. Inspect the stop lamp switch and adjust and/or calibrate if needed. Refer to Stop Lamp Switch Adjustment in Lighting Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 5 
5 
  1. Turn OFF the ignition.
  2. Disconnect the stop lamp switch connector.
  3. Connect a 3 amp fused jumper wire between the battery positive voltage circuit of the stop lamp switch and the signal circuit of the stop lamp switch.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, observe the Stop Lamp Switch parameter.
Does the scan tool display Applied?		 Go to Step 11  Go to Step 6 
6 Test the signal circuit of the stop lamp switch for an open between the splice pack of the stoplamp signal circuit and the EBCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 10 
7 Test the battery positive voltage circuit of the stoplamp switch for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 8 
8 Test the signal circuit of the stop lamp switch for an open between the stop lamp switch and the splice of the stop lamp signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 9 
9 Test the signal circuit of the stop lamp switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 14  Go to Step 10 
10 Inspect for poor connections at the harness connector of the EBCM. 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 14  Go to Step 12 
11 Inspect for poor connections at the harness connector of the stoplamp switch. 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 14  Go to Step 13 
12 Replace the EBCM. Refer to Electronic Brake Control Module Replacement .
Did you complete the repair?		 Go to Step 14  -
13 Replace the stop lamp switch. Refer to Stop Lamp Switch Replacement in Lighting Systems.
Did you complete the repair?		 Go to Step 14  -
14
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 Go to Step 2  System OK
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.