U059A: DC-DC Converter 'B' Data Invalid
The U059A code indicates that the DC-DC converter 'B' control module has transmitted invalid or erroneous data over the vehicle's CAN bus. This means the receiving module detected an anomaly in the integrity, format, or content of the message from the DC-DC converter 'B'. DC-DC converters step down the high-voltage traction battery (in hybrid/electric vehicles) to 12V for auxiliary systems and the standard battery. This communication fault prevents precise energy management, potentially affecting electrical load distribution.
1. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.
2. Most Common Causes
- Internal failure in the DC-DC converter 'B' control module
- Short circuit or open circuit in the CAN bus wiring (High/Low)
- Poor connection or corrosion at the DC-DC module connectors
- Missing 12V or high-voltage supply, or faulty ground to the DC-DC converter
- Electromagnetic interference (EMI) corrupting data signals
- Fault in the body control module (BCM) or powertrain control module (PCM) receiving the signal
3. Symptoms You Will Notice
- Battery warning light or check engine light illuminated
- Electrical system malfunctions (e.g., dim lights, weak accessories)
4. Step-by-Step Diagnosis
Scan for additional codes and verify U059A is active
Inspect DC-DC converter 'B' connectors for corrosion, damage, or loose pins
Test CAN bus wiring for shorts, opens, or high resistance between the converter and other modules
Check power and ground circuits to the DC-DC converter (both 12V and high-voltage supply)
If wiring and power are OK, suspect internal module failure and replace DC-DC converter 'B'
5. Frequently Asked Questions
Is it safe to drive?▼
No, it is not safe to drive. This code indicates a high-severity communication fault that can lead to unpredictable electrical system behavior, including loss of critical functions. The vehicle should be towed to a repair facility.
How much does it cost to fix?▼
Repair costs typically range from $200 to $1,200 USD, depending on the root cause. Simple wiring repairs may cost $200-$400, while replacing the DC-DC converter module can range from $600 to $1,200 including parts and labor.