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

What's Unique About the 2019-2020 Gmc ACADIA

This issue is a well-documented software problem specific to this generation of GM vehicles using the C1XX platform and the eBoost braking system, including the Acadia. Unlike many brake codes that point to a failed sensor or hydraulic part, C0024 is most often resolved with a software update rather than a hardware replacement. General Motors issued Technical Service Bulletin #20-NA-073 to address this exact condition across multiple vehicle lines.

Diagnostic Flowchart

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

Symptoms You May Notice

• Brake pedal is very hard to press
• Loss of power brake assist
• Brake pedal feels different or has longer travel
• Various warning messages on the Driver Information Center (DIC), such as 'Service Brake Assist'

Most Likely Causes

1. Brake System Control Module (BSCM) Software Glitch 🔴 High Probability A known software anomaly was present in the original module programming, as documented by GM in TSB #20-NA-073. The glitch involves an inaccurate calculation of solenoid temperature, which can cause the diagnostic to set incorrectly.
   How to confirm: A GM dealer or a qualified shop with access to GM's service information system can confirm TSB #20-NA-073 applies to the vehicle's VIN and that the required software update has not yet been performed.
   Typical fix: Reprogram the Brake System Control Module (BSCM) with the latest software version available through GM's Techline Connect system. This is a software-only repair.
   Est. part cost: $0

Rare But Worth Checking

• Failed Brake System Control Module (BSCM): In the rare event that the module fails to accept the new software or has an internal hardware failure, the entire module will need to be replaced. This should only be considered after a reprogramming attempt fails. Some other GM vehicles have experienced eBoost module failures due to material contamination during manufacturing, though this is covered under different service campaigns.

Diagnosis Steps

1. Confirm the presence of code C0024 using an OBD-II scanner capable of reading Chassis (C) codes.
2. Check for any other related trouble codes listed in TSB #20-NA-073, such as P0606 or C0021.
3. Verify the symptoms, specifically a hard brake pedal and 'Service Brake Assist' message.
4. Check for applicability of Technical Service Bulletin #20-NA-073 to the vehicle's VIN using a dealer or professional service information system.
5. If the TSB is applicable and has not been performed, the first and most direct step is to have a dealer reprogram the Brake System Control Module (BSCM).
6. During reprogramming, the technician must use a stable power supply to the vehicle to prevent module damage and must record a Warranty Claim Code (WCC) from the SPS software for the repair to be processed correctly under warranty.
7. If reprogramming does not resolve the issue, further diagnosis of the BSCM and its circuits is required, which may lead to module replacement.

Parts You'll Likely Need

• Electronic Brake Control Module (BSCM) (OEM #84401914) — This part is only needed in the rare case that a software re-flash does not fix the issue and the module itself is determined to be faulty. The primary fix is software, not hardware. Part number 84401914 supersedes the older 84329995.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $145-$255
  Aftermarket price range: $200-$350

Related Codes That Often Appear With This One

• P0606 — Indicates a general internal processor fault in a control module, often logged alongside the more specific C0024. TSB #20-NA-073 explicitly lists this code.
• C0021 — Relates to the brake booster performance, often triggered by the same underlying eBoost system fault. TSB #20-NA-073 explicitly lists this code.
• P25A2 — Brake Booster Pressure Sensor Circuit fault, which can be set as a consequence of the main BSCM issue. TSB #20-NA-073 explicitly lists this code.
• C05D2, C0595, C2A3B, C053D — These are other manufacturer-specific chassis codes that TSB #20-NA-073 notes may be set along with C0024 due to the same BSCM software issue.

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 document outlining the software cause and reprogramming fix.

Platform-Specific Known Issues

• A significant number of 2019-2020 GM vehicles, including the Acadia, were released with BSCM software that can trigger a false fault, leading to code C0024 and a loss of brake assist. This is formally addressed by TSB #20-NA-073.

Mechanic-Grade Diagnostic Values

• Brake Pedal Position (BPP) Sensor Voltage (at ECM) — expected: Approximately 1.0V +/- 0.3V with the brake pedal released.. Failure: Voltage that is significantly different from the 'BPP Sensor Learned Released Position' value stored in the ECM, or a voltage that doesn't change proportionally as the pedal is depressed.
• Brake Pedal Position (BPP) Sensor Percentage (at ECM) — expected: 0% with the brake pedal released.. Failure: A reading greater than 0% when the pedal is not being touched.

Hidden / Shadow Codes Worth Checking

• C0024 5A: The main code C0024 indicates an internal failure in the brake boost system. The symptom byte '$5A' provides more specific detail, indicating an 'Internal Electronic Failure'. This strongly points towards the software or internal hardware fault addressed by TSB 20-NA-073, rather than an external wiring or sensor issue. (see via A dealer-level scan tool like the GM MDI2 with GDS2 software is required to view symptom bytes.)

Scan Tool Commands That Help

• GM GDS2 (Global Diagnostic System 2): Module Diagnostics -> K17 Brake System Control Module -> Data Display — To view live data from the BSCM, such as sensor inputs and internal status, which can help confirm if the module is communicating and if its readings are plausible before attempting a reprogram.
• GM GDS2 (Global Diagnostic System 2): SPS (Service Programming System) -> Reprogram ECU — This is the specific function used to perform the software update on the Brake System Control Module as prescribed by TSB #20-NA-073. It requires a Techline Connect subscription.
• GM GDS2 (Global Diagnostic System 2): Data Bus Diagnostic Tool — If reprogramming fails and a communication issue is suspected, this tool can actively monitor the vehicle's data networks to identify which modules are online and if there are interruptions or faults on the bus.

Wiring & Ground Locations

• K17 — The Brake System Control Module (BSCM), also known as the Electronic Brake Control Module (EBCM), is the electronic control unit attached to the ABS hydraulic block in the engine compartment. 🎬 Watch: How to locate the brake pump and control module.. This is the module that sets code C0024 and requires the software update. All power, ground, and communication circuits terminate here.
• G303 — On the left front frame rail, near the front of the engine compartment. It serves as a primary ground point for several components in that area.. This is a common ground location for front-end modules. A corroded or loose G303 ground can cause erratic behavior and fault codes in the BSCM, although this is a much rarer cause for C0024 than the software issue. Checking this ground is a valid diagnostic step if reprogramming fails.
• X1 Connector — The main electrical harness connector at the Brake System Control Module (K17).. All power, ground, and communication signals for the module pass through this 38-pin connector. While unlikely to be the cause, checking for corrosion or backed-out pins here is a final step in diagnosing a module that fails to communicate or accept a reprogram.

Real Owner Repair Stories

• Acadia Forum User (2019 GMC Acadia) — Hard brake pedal, 'Service Brake Assist' warning light on the dash.
  ❌ Tried (didn't work) Initial diagnosis pointed to the brake booster.
  ✅ What actually fixed it The user took the vehicle to a GM dealer. The dealer identified TSB #20-NA-073 and performed the software reprogram on the Brake System Control Module. The issue was resolved and covered under the 8yr/80k mile emissions warranty.