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Home >> Chevrolet >> 2021 >> Blazer RS, FWD >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Hydraulic Brakes >> Diagnostic Information and Procedures >> DTC C0021 >> Circuit/System Verification

Circuit/System Verification

  1. Verify DTC C05B0 is not set.
    • Go to next step: If the DTC is not set 
  2. Ignition/Vehicle - Off = 10 s - Brake Pedal = Not applied
  3. Ignition - On/Vehicle - In Service Mode
  4. NOTE:

    If the Brake Hydraulics Test still fails after performing the Hydraulic Brake System Bleeding (Manual without JEO) , or Hydraulic Brake System Bleeding (Pressure without JEO) , or Hydraulic Brake System Bleeding (Pressure with JEO)  at least 3 times, performing the scan tool control function test Brake System Hydraulics Corner Test can be performed to help isolate the concern.

  5. Perform the scan tool control function: Brake Hydraulics Test

    Perform the scan tool control function: Brake Hydraulics Test

    • Go to next step: If the procedure/test passes 
  6. Verify DTC C0021 is not set.
    • If DTC C0021 is set 

      Replace the component: A104 Brake Master Cylinder

    • Go to next step: If the DTC is not set 
  7. All OK.