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Home >> Pontiac >> 2006 >> GTO Standard >> Repair and Diagnosis >> Brakes >> Antilock Brake System With Traction Control System >> Diagnostic Information and Procedures >> DTC C0121 >> Test Description

Test Description

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

  1. 5:  This step tests the EBCM ground circuit for an open, or high resistance.
  2. 6:  This step tests the battery supply voltage circuits of the EBCM for an open, high resistance or short to ground.
DTC C0121

Step Action Yes No
Schematic Reference:  Antilock Brake System Schematics  
Connector End View Reference:  Antilock Brake System Connector End Views  
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. Use the scan tool in order to clear the DTCs.
  4. Using the scan tool, perform the hydraulic modulator solenoid valve test in the special functions menu.
Did the test pass?		 Go to Step 3  Go to Step 4 
3
  1. Install a scan tool.
  2. Use the scan tool in order to clear the DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Did DTC C0121 reset?		 Go to Step 4  Go to Diagnostic Aids
4 Is DTC C0800 also set? Go to DTC C0800  Go to Step 5 
5  Test the electronic brake control module (EBCM) ground circuit for an open, or high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 9  Go to Step 6 
6  Test the EBCM battery supply voltage circuits for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 9  Go to Step 7 
7 Inspect for poor connections at the harness connector for 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 9  Go to Step 8 
8 Replace the brake pressure modulator valve (BPMV) assembly. Refer to Brake Pressure Modulator Valve (BPMV) Replacement .
Did you complete the replacement?		 Go to Step 9  -
9
  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
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