A failing DC/DC Converter Control Module A, typically due to internal component degradation or heat damage; Corroded, loose, or damaged wiring and connectors in the converter's power or communication circuits; Low or unstable 12-volt battery voltage causing the converter module to transmit corrupted data; A software or calibration fault in the converter module or the supervising module; Poor ground connections shared by the converter and the network gateway; Electrical interference from a failing alternator or high-voltage component corrupting bus signals; A fault in the communication bus itself, such as a shorted or open data line, that distorts the converter's messages

DTC codes / U05xx · Network communication / U0599

U0599Invalid Data Received From DC/DC Converter Control Module A

Q: What does code U0599 mean?

Invalid Data Received From DC/DC Converter Control Module A. U0599 means the module that supervises the vehicle's communication networks received data from the DC/DC Converter Control Module A that it judged invalid or corrupted. The supervising module did not lose contact with the converter; it saw messages arriving with impossible values, failed checksums, or out-of-range signals, so it flagged the data itself as untrustworthy.

U0599 means the module that supervises the vehicle's communication networks received data from the DC/DC Converter Control Module A that it judged invalid or corrupted. The supervising module did not lose contact with the converter; it saw messages arriving with impossible values, failed checksums, or out-of-range signals, so it flagged the data itself as untrustworthy.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaNetwork communication

Symptoms you may notice

Illumination of the check engine light or a dedicated service vehicle message
A warning lamp or message indicating a charging system or high-voltage system fault
Reduced or disabled accessory power, such as a dead 12-volt outlet or inoperative interior lighting
The vehicle may refuse to start or may enter a reduced-power mode if the converter is part of a hybrid or electric system
Often no symptoms besides the warning light, with the vehicle driving normally
Intermittent electrical oddities in multiple modules that share the same communication bus

Common causes, most likely first

A failing DC/DC Converter Control Module A, typically due to internal component degradation or heat damage
Corroded, loose, or damaged wiring and connectors in the converter's power or communication circuits
Low or unstable 12-volt battery voltage causing the converter module to transmit corrupted data
A software or calibration fault in the converter module or the supervising module
Poor ground connections shared by the converter and the network gateway
Electrical interference from a failing alternator or high-voltage component corrupting bus signals
A fault in the communication bus itself, such as a shorted or open data line, that distorts the converter's messages

How to diagnose and fix it

Perform a full scan of all modules and record every stored and pending code before clearing anything
Check battery voltage and charging system output; a weak battery is a common source of invalid data
Inspect the DC/DC converter connectors and harness for corrosion, chafing, and loose pins
Verify the converter's ground and power feeds with a multimeter under load
Check the communication bus integrity with an oscilloscope or a bus health test if the scan tool supports it
If wiring and power are sound, follow the manufacturer's diagnostic flow for the converter module, including any software updates
Replace the DC/DC Converter Control Module A only after all external causes are ruled out, then clear codes and verify the repair

What the invalid data really means

U0599 does not mean the converter module is dead; it means the supervising module rejected the data it sent, so a module that still powers accessories can set this code.
A weak 12-volt battery is frequently the real culprit because the converter module may boot and transmit before its supply is stable, producing invalid frames.
Technicians often replace the converter only to find a corroded ground or a chafed harness near the converter was corrupting the bus signal.
This code can appear after jump-starting or battery replacement when voltage transients disturb the network, and it may clear itself after a few clean drive cycles.
On hybrid and electric vehicles, the DC/DC converter is part of the high-voltage system, so invalid data can also trigger high-voltage isolation or charging faults in other modules.

Can I keep driving with U0599?

If the vehicle drives normally and only the warning light is on, you can drive cautiously to a repair shop, but avoid long trips and heavy electrical loads. If the converter supplies the 12-volt system on a hybrid or electric vehicle, a failure can leave you stranded, so have it checked promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.