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Tahoe / Yukon Service Manual

DTC C0021

Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC C0021 Brake System Performance Symptom Byte Information: Symptom Byte List Circuit/System Description For an overview of the component/system, refer to: Hydraulic Brake System Description and Operation Conditions for Running the DTC Ignition/Vehicle = OFF Conditions for Setting the DTC Ignition Off = Incomplete The above conditions must occur for 10 consecutive ignition cycles. Actions Taken When the DTC Sets Brake warning indicator malfunction. = ON ABS Indicator Control = ON Traction/Stability Control Indicator = ON Malfunction Indicator Lamp (MIL) = ON A message and/or warning indicator may be displayed to the driver. Vehicle Speed Limit = Less than 100 km/h (62 MPH) Malfunction Indicator Lamp (MIL) = ON Brake Assist = None DTCs listed in the DTC Descriptor category = Type A DTC Conditions for Clearing the DTC The conditions for setting the DTC no longer exist. A history DTC will clear after 40 consecutive malfunction-free ignition cycles. DTCs listed in the DTC Descriptor category = Type A DTC Diagnostic Aids If during testing the Brake Hydraulics Test still fails after performing the Hydraulic Brake System Bleeding at least 3 times, performing the scan tool control function test Brake System Hydraulics Corner Test can be performed to help isolate the concern. The Brake System Hydraulics Corner Test is not to be used in place of the Brake Hydraulics Test. Inspect the calipers, check for worn or tapered pads, seized pistons or guide pins. Refer to: Disc Brake System Diagnosis Reference Information Schematic Reference Antilock Brake System Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References Circuit/System Verification

  1. Verify DTC C05B0 is not set. ⇒ If DTC C05B0 is set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If the DTC is not set
  2. Perform the Scan Tool Configuration/Reset Functions — Brake System Plunger Motor Position Sensor Learn
  3. Clear DTCs
  4. Verify DTC C0021 is not set. ⇒ If the DTC is not set All OK. ⇓ If DTC C0021 is set
  5. Ignition/Vehicle » Off = 10 s — Brake Pedal = Not applied
  6. Ignition » On / Vehicle » In Service Mode
  1. Perform the scan tool control function: Brake Hydraulics Test Perform the scan tool control function: Brake Hydraulics Test ⇒ If the procedure/test does not pass Refer to: Hydraulic Brake System Bleeding ⇓ If the procedure/test passes
  2. Verify DTC C0021 is not set. ⇒ If DTC C0021 is set Replace the component: A104 Brake Master Cylinder ⇓ If the DTC is not set
  3. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Brake Master Cylinder Replacement - With Power Brake Booster and Electronic Brake Control Module For control module replacement, programming, and setup refer to: Control Module References