What it means
A receiving control module has detected invalid data from DC/DC Converter Control Module A. The code does not specify which data is invalid or why.
How it works
DC/DC Converter Control Module A manages conversion of high-voltage direct current to the lower-voltage supply used by vehicle electronics in vehicles equipped with this system. U0599 sets when another module rejects data from converter controller A as invalid, which can accompany problems with low-voltage supply or network communication.
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, low-voltage, converter, and communication codes to see whether other modules report supply or network problems.
- Check the 12-volt battery and charging behavior using the vehicle’s specified procedure, since DC/DC operation supports the low-voltage system.
- Inspect controller A’s accessible low-voltage connectors and harness for looseness, corrosion, damage, or recent repair work.
- Use a scan tool to compare controller A status and reported conversion data with low-voltage system readings.
- Check gateway and communication codes, then test controller A’s low-voltage power, ground, and data circuits to the manufacturer’s specification.
- If the converter controller or another module was replaced or programmed, verify software and configuration compatibility before replacing parts.
Common fixes
- Repair damaged or corroded low-voltage connectors or wiring at DC/DC converter control module A.
- Correct a weak 12-volt battery or related low-voltage charging problem.
- Apply the correct software or configuration if a mismatch is confirmed.
- Repair a gateway or network fault identified by circuit testing.
- Replace DC/DC converter control module A only if checks confirm an internal fault.
Can I keep driving?
If the vehicle reports a low-voltage or charging warning, or electrical systems begin shutting down, stop safely and follow the vehicle’s instructions; continued operation could drain the 12-volt supply and leave the vehicle unable to operate. Do not handle high-voltage wiring.
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.