C056D on GMC
Electronic Brake Control Module Internal Fault (manufacturer-specific)
C056D on GMC vehicles indicates electronic brake control module internal fault (manufacturer-specific). Au7o has documented this code across 1 GMC model — most commonly on Sierra 3500HD. C056D is a manufacturer-specific chassis code (frequently seen on GM vehicles) that generally indicates an internal hardware/electronics failure within the electronic brake control module (EBCM)/ABS assembly. When the module's own self-test detects a fault it cannot recover from, it disables ABS, traction control, and stability control and commonly triggers the 'Service StabiliTrak'/'Service Traction Control' messages. Because the fault is internal to the module, the usual repair is reprogramming or replacing the ABS/EBCM unit after confirming wiring and power/ground are good. Conventional braking still functions while the electronic aids are offline.
Common Causes of C056D
- •Internal EBCM/ABS module hardware failure
- •Corroded or damaged module connector/pins
- •Poor power or ground to the ABS module
- •Low battery voltage or charging system issues
- •Water intrusion/corrosion in the module
- •Module software/calibration corruption
- •Wiring faults at the brake module connector
C056D on GMC by Model
GMC Sierra 3500HD(1 issue)
- Electric power steering (EPS) assist loss / reduced assist warnings (new body style)2020-2024
On 2020+ Sierra 3500HD (T1 platform) with electric power steering, owners report intermittent loss of steering assist and warning messages such as "Steering Assist Reduced". NHTSA complaints and GM service information commonly point to EPS module/software issues, wiring/connector concerns, or rack-related faults that can occur without prior symptoms.
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View C056D across all makes →Frequently Asked Questions
What does C056D mean on GMC?▼
C056D stands for "Electronic Brake Control Module Internal Fault (manufacturer-specific)." C056D is a manufacturer-specific chassis code (frequently seen on GM vehicles) that generally indicates an internal hardware/electronics failure within the electronic brake control module (EBCM)/ABS assembly. When the module's own self-test detects a fault it cannot recover from, it disables ABS, traction control, and stability control and commonly triggers the 'Service StabiliTrak'/'Service Traction Control' messages. Because the fault is internal to the module, the usual repair is reprogramming or replacing the ABS/EBCM unit after confirming wiring and power/ground are good. Conventional braking still functions while the electronic aids are offline. On GMC specifically, this code is documented across 1 model.
What causes C056D on GMC vehicles?▼
Common causes on GMC: Internal EBCM/ABS module hardware failure, Corroded or damaged module connector/pins, Poor power or ground to the ABS module, Low battery voltage or charging system issues, Water intrusion/corrosion in the module. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix C056D on a GMC?▼
Repair costs vary widely depending on the root cause and specific GMC model.
Which GMC models have C056D documented?▼
Au7o has documented C056D on 1 GMC model: Sierra 3500HD.