What it means
A receiving control module has detected invalid data from DC/DC Converter Control Module B. The code does not specify which data is invalid or why.
How it works
The DC/DC converter control module B manages conversion of high-voltage power to lower-voltage power for vehicle systems. Another module checks the data it receives from controller B and sets U059A when that data fails validity checks; the code alone does not identify the bad value or its cause.
Common causes
Most likely first.
- Module internal fault or sensor input drift
- Software version mismatch after replacement
- Gateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan all modules and save freeze-frame or event data to identify which module logged U059A and whether other communication codes appeared at the same time.
- Check the 12-volt battery and charging condition because unstable supply voltage can disrupt messages from the DC/DC converter controller.
- Inspect controller B's connectors, grounds, and harness for looseness, corrosion, moisture, or damage.
- Compare available live data from controller B with related power-conversion and vehicle-voltage readings for missing or implausible values.
- If wiring and power are sound, check whether controller B or the gateway was recently replaced or updated and verify compatibility and calibration.
- If the fault returns, test the relevant network wiring and message routing using the manufacturer's diagnostic procedure before considering a controller fault.
Common fixes
- Repair damaged wiring or clean and secure controller B's connector and ground.
- Correct a weak 12-volt battery or charging-system problem affecting module communication.
- Update or configure a recently replaced controller or gateway to the vehicle's required software.
- Replace DC/DC converter control module B only after its supply, network, and data validity have been checked.
Can I keep driving?
If the vehicle has warnings, reduced power, or charging problems, limit driving and stop if it becomes difficult to control or electrical systems begin shutting down. A DC/DC converter fault can impair low-voltage power supply and leave the vehicle unable to operate reliably.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.