U0599Invalid Data Received From DC/DC Converter Control Module A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- On start-stop vehicles a DC/DC converter can hold the 12 V supply for sensitive electronics while the starter pulls the voltage down; on hybrids it feeds the 12 V network from the high-voltage battery. GM's 2025 engine tables check the converter's output voltage and crank-control messages for alive counter, protection value and checksum errors and set U0599, Type B, after 8 failures in 18 samples with at least 11 V for 5 s. GM bulletin 20-NA-191 for the 2020 Cadillac CT4 and CT5 with auto start/stop shows the code set falsely: the ECM miscalculated the protection value during cranking without boost, disabled start-stop on the first failure and lit the MIL on the second; an ECM reprogram fixed it. FCA lists U0599 for the 2019 Cherokee V6 ESS; Ford's 2014 list has it without MIL.
- What you may notice
- Auto start/stop disabled
- Check engine light after repeated failures
- Likely causes
- LikelyEngine controller software miscalculating the converter's protection value (GM 20-NA-191)
- PossibleDC/DC converter A electronics faulty
- RareWeak 12 V battery causing deep voltage dips during cranking
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.