U357B on Cadillac: How to Diagnose & Fix
Manufacturer-specific network code (definition unverified)
1 Cadillac model · 1 documented issue
U357B on Cadillac by model: symptoms, diagnosis and fix
GM bulletin 23-NA-124 covers a dead 12V battery, no-start, inoperative passive-key functions and parasitic draw on the 2023 Lyriq when a Serial Data Gateway Module software anomaly keeps activity alive. PIP6021 separately covers 2023-2024 Lyriq discharge only when its complete listed BECM DTC set is present.
Common Symptoms
- Dead or discharged 12V battery
- No start
- Passive key functions unavailable
- Parasitic draw
How to Fix
Have an EV-qualified Cadillac technician reproduce the draw and scan every module. For the 2023 gateway condition, cycle the specified fuse and verify or update the gateway software. Apply PIP6021 only when all listed DTCs are present; otherwise continue normal service-information diagnosis. Accept applicable future OTA updates. Do not disconnect the 12V or high-voltage system from this card.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (2)
U357B 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 U357B mean on a Cadillac?
U357B stands for "Manufacturer-specific network code (definition unverified)." This code appears in real manufacturer service material - it shows up in a General Motors technical service bulletin hosted by NHTSA alongside other U-series codes - but a verified definition could not be established from a reliable source. U-range codes generally indicate a network or module communication fault rather than a mechanical failure. Because the exact meaning is manufacturer-specific, it must be read with a scan tool that supports the vehicle's make, or looked up in the manufacturer's own service information. On Cadillac it is documented across 1 model: Lyriq.
What are the most common causes of U357B?
The most common causes of U357B are: Definition not verified - causes cannot be responsibly listed, Requires manufacturer-specific service information or a dealer-level scan tool. The specific cause varies by vehicle.
How much does it cost to fix U357B on a Cadillac?
Repair costs vary widely with the root cause and Cadillac model; each issue on this page carries its own estimate where one is published.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.