P3055 on Buick: How to Diagnose & Fix
DC/DC Converter Actuator Voltage 1 Performance (GM)
1 Buick model · 1 documented issue · 1 critical
P3055 on Buick by model: symptoms, diagnosis and fix
GM recalled certain 2016 Regals (built Aug 2015 – Feb 2016) because a defective circuit board in the electric belt-drive rack-and-pinion steering gear could cause a sudden loss of power steering assist, sharply increasing steering effort and crash risk. Owners have also reported steering jolting or locking at speed. Beyond the formal recall, electric power steering faults (e.g., P3055/P3056 'Steering Assist Reduced' messages) are reported on later Regals.
Common Symptoms
- 'Steering Assist Reduced' warning message
- Sudden heavy/stiff steering
- Steering jolting or pulling to one side
- Loss of power assist at speed
How to Fix
Under recall 21510, dealers replace the electric belt-drive rack-and-pinion steering gear assembly free of charge. Non-recall failures require diagnosis of the steering rack motor/module and replacement.
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Sources for this issue (1)
P3055 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 P3055 mean on a Buick?
P3055 stands for "DC/DC Converter Actuator Voltage 1 Performance (GM)." P3055 is a manufacturer-specific code defined primarily by General Motors (Chevrolet, Buick, GMC) on vehicles with the auto stop/start system, such as the 2016-2021 Malibu, 2018-2021 Equinox, Blazer, Encore, and 2019-2021 Silverado/Sierra. When the engine shuts off at a stop, a DC/DC converter (GM calls it the Multifunction Power Supply Converter) boosts and stabilizes 12-volt power so the radio, instrument cluster, and electric power steering keep working; P3055 sets when the engine control module sees that converter's output voltage 1 fall out of spec, and it usually appears together with P3056. Drivers typically notice a check engine light with auto stop/start and remote start disabled, and sometimes flickering electronics, battery drain, or stalling during an auto-stop event. The car generally remains drivable, but ignoring it leaves the underlying battery, ground, or converter problem to worsen, which can lead to electrical glitches or a no-start. GM addressed this code in TSBs 18-NA-247 (poor ground connections) and 21-NA-139 (converter module replacement). Note: despite occasional association with Toyota/Lexus hybrids, Toyota's hybrid battery block codes run P3011-P3024 and P3055 is not documented among them; a few other manufacturers assign unrelated meanings to this code (e.g., a seat potentiometer circuit fault on some VW Touareg listings). On Buick it is documented across 1 model: Regal.
What are the most common causes of P3055?
The most common causes of P3055 are: Failed DC/DC converter module (Multifunction Power Supply Converter, e.g., GM part 13514044 Malibu / 13510484 Equinox) — the most frequent fix per TSB 21-NA-139, Weak or failing main 12V AGM battery — load-test it before replacing the converter, Poor or corroded ground connections (G104, G107, G108) — addressed by GM TSB 18-NA-247, Failed or degraded auxiliary 12V battery (trunk-mounted on some models) that supports stop/start events, Damaged wiring or loose connectors in the DC/DC converter circuit, Incorrectly installed factory fuses in slots F51DR/F52DR on 2019-2021 Silverado/Sierra, DC/DC converter module misconfiguration or outdated programming. The specific cause varies by vehicle.
How much does it cost to fix P3055 on a Buick?
Repair costs vary widely with the root cause and Buick model; each issue on this page carries its own estimate where one is published.
Looking for P3055 on a different make?
View P3055 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.