C0024 on 2019-2020 GMC Sierra 1500: Brake Assist Failure Causes and Fixes

What's Unique About the 2019-2020 Gmc SIERRA 1500

The 2019-2020 Sierra 1500, part of the T1 platform, uses a sophisticated electronic brake booster ('eBoost') that is highly dependent on software. Unlike older vacuum-based systems, a software anomaly can disable power braking entirely, even if the mechanical and hydraulic components are perfectly fine. This specific vulnerability is not a hardware failure but a logic error. GM issued Technical Service Bulletin 20-NA-073 to correct the logic in the Brake System Control Module (BSCM) via a software update, rather than replacing the expensive eBoost assembly.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Loss of power brake assist, requiring very high pedal effort
• Brake pedal feels hard, stiff, or has a longer/softer travel than normal
• Multiple warning messages in the Driver Information Center (DIC), such as 'Service Brake Assist 🎬 See what the Service Brake Assist warning actually means', 'Service ESC', 'Brake System Failure'
• Brake system warning light is illuminated
• Vehicle may enter a limp mode with a maximum speed warning, such as 'Top Speed Limited to 43 MPH 🎬 Watch: How to reset the 43 MPH limp mode message'
• ABS and Traction Control/ESC warning lights illuminated

Most Likely Causes

1. Brake System Control Module (BSCM) Software Error 🔴 High Probability → Shop ABS Control Module A known software issue causes the module to incorrectly diagnose a fault due to a discrepancy between the calculated and actual solenoid temperature, and a correlation error between motor position sensors, as documented in TSB 20-NA-073.
   How to confirm: A GM dealer or qualified shop with access to GM's Service Programming System (SPS) must check the current software calibration on the BSCM (K160) and compare it to the latest version available. The TSB is the definitive confirmation.
   Typical fix: Reprogramming the Brake System Control Module (BSCM) with updated software. This is a dealer-level procedure that must be done with a hardwired internet connection and a stable vehicle voltage supply.
   Est. part cost: $0

Rare But Worth Checking

• Wiring Harness or Connector Issue: While the TSB points to software, physical damage to wiring leading to the brake control module or wheel speed sensors can cause similar warnings and codes. Check for corrosion or damage, especially if the vehicle has been in an accident or driven in harsh conditions. A user on Reddit reported a similar cluster of brake warnings on a newer Sierra that was traced to a faulty engine wiring harness.
• Failing Brake System Control Module (BSCM): → Shop ABS Control Module In rare cases where the software update does not resolve the issue, the module itself may have an internal hardware failure. This is an expensive last resort. A related Customer Satisfaction Program (N202324120) for 2021 models involved replacing the entire eBoost unit for potential function issues.
• Low Battery Voltage / Electrical System Fault: Modern electronic modules are sensitive to voltage. A weak battery or intermittent connection, such as the one described in recall 19V888000 for a loose alternator cable, could potentially trigger module faults. The TSB for the C0024 fix specifically warns that stable battery voltage is critical during reprogramming, highlighting the system's sensitivity. A separate TSB (PIT6474A) for 2022-2024 models notes that a voltage drop during cranking can set codes P0562 and P0606 in the BSCM, causing loss of brake assist, reinforcing the system's voltage sensitivity.

Diagnosis Steps

1. Confirm the presence of code C0024 using a high-quality OBD-II scanner capable of reading Chassis (C) codes.
2. Verify the symptoms: test for a hard brake pedal and loss of power assist (in a safe, controlled environment). Note all warning messages on the DIC.
3. Contact a GM dealership with your VIN to check if TSB 20-NA-073 has been performed on your vehicle. This is the most critical step.
4. If the TSB has not been performed, the primary repair is to have the dealer reprogram the Brake System Control Module (BSCM). The technician must follow the TSB procedure exactly, including using a stable power supply and a wired network connection.
5. If the TSB has been performed or does not fix the issue, a technician should inspect the wiring and connectors for the BSCM and wheel speed sensors for any signs of damage, corrosion, or looseness. 🎬 Watch: How to enter brake service mode for safe maintenance Pay special attention to main body and engine harness grounds G110 and G114, as loose connections are a known issue on these trucks.
6. Perform a full vehicle battery and charging system test. The eBoost system is highly sensitive to voltage fluctuations. Ensure all battery cable connections are clean and tight.
7. As a final step, if all else fails and the software and wiring are confirmed good, the BSCM itself (as part of the eBoost assembly) may need to be diagnosed and potentially replaced.

Parts You'll Likely Need

• Brake System Control Module (BSCM) Reprogramming — This is not a physical part, but a software update that corrects the logic error causing the false fault code, as specified by GM TSB 20-NA-073.
  OEM price range: $150-$300 (Labor for programming)
  Aftermarket price range: N/A
• Brake Master Cylinder w/ BSCM (eBoost Unit Assembly) (OEM #84926778 (with trailer braking, JL1) or 84926779 (without JL1)) — This part is only needed in the rare event that reprogramming fails and the module itself is diagnosed with an internal hardware fault. These part numbers are from a related 2021 model year campaign but illustrate the assembly that would be replaced.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $600-$900
  Aftermarket price range: $400-$700

Related Codes That Often Appear With This One

• C05D2 — This code for 'Brake Master Cylinder Piston Excessive Travel' is also related to the eBoost system and is mentioned in the same TSB (#20-NA-073) as C0024.
• P25A2 — This powertrain code for 'Brake Booster Pressure Sensor Circuit' is often set alongside chassis codes like C0024 when the eBoost system faults.
• C0021 — Another brake system-related code listed in TSB #20-NA-073, indicating a broader fault within the electronic brake control system.
• P0606 — This code for 'Control Module Processor Performance' is explicitly listed alongside C0024 in revised versions of TSB 20-NA-073, indicating a processor-level fault detection within the BSCM.
• C0595 — Listed in TSB 20-NA-073, this code points to an 'Internal Driver Performance' issue within the Brake System Control Module.

Technical Service Bulletins (TSBs) & Recalls

• 20-NA-073: 'Loss of Brake Assist, Various Messages Displayed in Driver Information Center (DIC), Brake Pedal Travel and Apply May Feel Different, DTC C0024 Set.' This TSB is the primary source for the cause (software error) and fix (BSCM reprogram). Multiple revisions expanded the list of affected vehicles and associated DTCs.

Platform-Specific Known Issues

• A widespread software issue on 2019-2020 GM trucks and SUVs with the eBoost system is the primary cause for this code, addressed by TSB 20-NA-073.
• A separate but related recall for some 2019 models involved a faulty software update (for a different issue) that could also disable electronic brake assist, particularly after a remote start, requiring another reprogram.

Scan Tool Commands That Help

• GDS2 (GM Global Diagnostic System 2): Module Diagnostics > K160 Brake System Control Module — To access DTC records, live data, and control functions specific to the eBoost system. This is the primary entry point for diagnosing the BSCM.
• GDS2 (GM Global Diagnostic System 2): Vehicle DTC Information — To perform a full vehicle scan and identify all codes stored in every module, which is crucial as C0024 is often accompanied by codes in other systems.
• GDS2 (GM Global Diagnostic System 2): Configuration/Reset Functions > Reprogram ECU — This function, used with the Service Programming System (SPS), is required to perform the software update specified in TSB 20-NA-073.

Wiring & Ground Locations

• G110 / G114 — Engine and body harness grounds located in the engine bay.. GM issued an engineering information bulletin (PIE0548) specifically requesting technicians to document and photograph loose connections at grounds G110 and G114 on 2019-2020 Sierra/Silverado trucks. A poor ground here can cause a variety of electrical faults, including module malfunctions that could trigger C0024.
• K160 Brake System Control Module Connector — The main electrical connector on the eBoost assembly, which includes the BSCM.. All power, ground, and communication signals for the eBoost system pass through this 38-way connector. Verifying pin integrity, checking for corrosion, and performing pin-out tests for voltage and ground are critical steps if a software update does not resolve the code.
• Engine Block to Chassis Ground — A braided ground strap typically running from the rear of the engine block to the vehicle's firewall/chassis.. This is a main ground path for the engine and its associated electronics. Corrosion or a break in this strap can cause unstable voltage and trigger faults in sensitive modules like the BSCM. Technicians often check this ground when diagnosing widespread electrical issues.

Real Owner Repair Stories

• gm-trucks.com Forum (2019 GMC Sierra) — Multiple warnings on the dash including 'Brake System Failure', 'Service ESC', and 'Service Trailer Brake System', accompanied by a complete loss of power brake assist.
  ❌ Tried (didn't work) The user did not report trying other fixes before going to the dealer.
  ✅ What actually fixed it The dealership performed the software update outlined in TSB 20-NA-073. The user reported that the dealer "reprogrammed the Brake control pack module" and this completely resolved all symptoms and warning lights.
• Reddit r/ChevyTrucks (2020 Chevy Silverado 1500) — 'Service Brake Assist', 'Brake System Failure', 'Service ESC' messages, and a speed limit of 43 MPH after performing a brake job and replacing a caliper.
  ❌ Tried (didn't work) Initial brake bleeding procedure.
  ✅ What actually fixed it The user drove the truck slowly for a few miles, shutting it off and restarting it several times. The brakes eventually started working correctly and all lights except the Check Engine Light turned off. A shop then cleared the remaining code. Another user in the same thread advised a specific reset procedure: put the truck in brake service mode, disconnect the battery, perform the brake work, pump the brakes, reconnect the battery, and then take it out of service mode.