C056E on Buick: How to Diagnose & Fix
Electronic Control Unit Software (Power Steering Control Module)
1 Buick model · 1 documented issue · 1 critical · $200-$1,500 repair
C056E on Buick by model: symptoms, diagnosis and fix
Envision owners report the steering going completely heavy or the wheel effectively locking, sometimes at highway speed during a merge and sometimes on the restart phase of the auto stop/start cycle. One NHTSA complaint describes total loss of assist lasting about five minutes that only cleared after an engine restart; another describes needing extreme force to regain control at 50 mph. GM TSB 17-NA-340 covers power steering service messages with loss of assist and DTC C056E-5A, and attributes it to the Smooth Road Shake Compensation algorithm in the power steering module software rather than a mechanical rack failure.
Common Symptoms
- Steering suddenly becomes extremely heavy or locks up
- Power steering warning message on the driver information center
- Loss of assist right after auto stop/start restarts the engine
- Assist returns only after shutting the engine off and restarting
How to Fix
Retrieve C056E-5A and follow GM TSB 17-NA-340, whose correction is to reprogram the power steering control module. Also verify battery and charging system output is stable (low voltage on stop/start restart is a common trigger), and inspect the power steering control module supply/ground circuit and connector if the fault returns after reprogramming. Full steering gear replacement is only warranted after the circuit and software are ruled out.
Sources for this issue (2)
C056E code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does C056E mean on a Buick?
C056E stands for "Electronic Control Unit Software (Power Steering Control Module)." General Motors chassis code stored by the Power Steering Control Module (PSCM). It reports a software/calibration integrity problem inside the steering control unit rather than a failed external sensor: the module either has no valid calibration data set, has a corrupt or mismatched calibration, or fails an internal software integrity check. The best-documented case is symptom 42 (calibration data set not programmed), which GM describes as latching when a steering gear assembly is installed without being programmed through SPS — the steering feels normal at first, then the module latches the fault and drops assist. Other symptom suffixes cover other internal software/calibration faults. When the code latches the PSCM stops providing assist, leaving heavy manual steering. On Buick it is documented across 1 model: Envision.
What are the most common causes of C056E?
The most common causes of C056E are: Steering gear / rack or PSCM replaced without SPS programming and calibration (symptom 42), Corrupt or interrupted software update to the power steering module, Outdated PSCM software requiring a reflash per a GM bulletin, Low or unstable supply voltage / poor power and ground at the PSCM causing failed writes, Internal PSCM failure requiring replacement of the steering gear assembly. The specific cause varies by vehicle.
How much does it cost to fix C056E on a Buick?
Published repair estimates on Buick range from $200 to $1,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for C056E on a different make?
View C056E across all makes →Join 700+ subscribers following Au7o for vehicle insights and updates.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.