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DTC codes / U05xx · Network communication / U059A

U059AInvalid Data Received From DC/DC Converter Control Module B

U059A is a communication fault that sets when a control module receives data from the DC/DC Converter Control Module B that it considers invalid or corrupted. The receiving module detects that the serial data message is missing expected parameters, contains out-of-range values, or fails its internal checksum, so it flags the data as untrustworthy rather than treating it as a valid signal.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaNetwork communication

Symptoms you may notice

  • The check engine light or service vehicle soon message illuminates on the dashboard.
  • Often no symptoms besides the warning light, especially if the DC/DC converter continues to function normally.
  • A warning message on the instrument cluster indicating a charging system or power supply fault.
  • Electrical accessories may behave erratically, such as flickering interior lights or intermittent infotainment resets.
  • The vehicle may enter a reduced-power or limp mode if the invalid data affects high-voltage system management.
  • Battery charging may be inconsistent, leading to a discharged 12-volt battery over time.

Common causes, most likely first

  1. A failing or degraded DC/DC Converter Control Module B, often due to internal electronic faults or heat damage.
  2. Corroded, loose, or damaged wiring and connectors in the controller area network (CAN) bus circuit between the DC/DC converter and the receiving module.
  3. Low or unstable 12-volt battery voltage or a weak charging system that causes modules to send corrupted data.
  4. A software or calibration issue in the DC/DC converter control module that requires a reflash or update.
  5. Water intrusion or physical damage to the DC/DC converter module or its harness, common in hybrid and electric vehicles.
  6. A faulty ground connection shared by the DC/DC converter and other modules, causing voltage offsets that corrupt data.
  7. Another module on the same CAN bus flooding the network with errors, indirectly causing the DC/DC converter data to be flagged as invalid.

How to diagnose and fix it

  1. Perform a full scan of all modules to record stored, pending, and permanent codes, and note any related communication or voltage codes.
  2. Inspect the 12-volt battery state of charge and charging system output, as low voltage is a frequent cause of invalid data codes.
  3. Visually inspect the DC/DC converter module and its harness connectors for corrosion, loose pins, chafed wires, or water intrusion.
  4. Check the CAN bus integrity with a multimeter or oscilloscope, looking for correct resistance and signal waveform at the DC/DC converter connector.
  5. Verify power and ground supplies at the DC/DC converter control module, including voltage drop tests on the ground circuit.
  6. If wiring and power are good, check for technical service bulletins or software updates for the DC/DC converter module and perform a reflash if available.
  7. Substitute a known-good DC/DC converter control module only after all electrical checks pass, then clear codes and verify the fault does not return.

Why invalid data is not always a bad converter

  • A weak or failing 12-volt battery is one of the most common root causes of U059A, because low voltage can cause the DC/DC converter to transmit corrupted data that the receiving module rejects.
  • The code does not automatically mean the DC/DC converter is defective; a poor ground connection or a damaged CAN bus wire can produce the same invalid data flag.
  • On hybrid and electric vehicles, the DC/DC converter often shares a coolant loop with other high-voltage components, and a coolant leak or air pocket can cause overheating and intermittent data faults.
  • Technicians sometimes replace the DC/DC converter only to find the code returns because a different module on the same bus is corrupting network traffic, so always check for other communication codes first.
  • A software calibration issue in the DC/DC converter can set U059A without any hardware failure, and a simple reflash may resolve it after all wiring checks pass.

Can I keep driving with U059A?

You can usually drive the vehicle short distances to a repair shop, but avoid long trips or heavy electrical loads because the DC/DC converter may not be charging the 12-volt battery reliably. If the vehicle enters limp mode or shows a charging system warning, stop driving and arrange a tow to prevent a breakdown.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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

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