P0A94: DC-DC converter fault
P0A94 means a fault in the DC-DC converter. That is the part that takes power down from the traction battery to keep the 12 volt battery topped up: the alternator's job on an electric car. Have it checked soon, because a flat 12 volt battery means a car that will not wake, however full the pack is.
Can you keep driving?
Usually in the short term, but book it soon. If the 12 volt battery is not being kept charged, the next stop can be a car that will not wake up.
What the code actually means
P0A94 points at the DC-DC converter itself, or at its control. On some cars it is shown as manufacturer specific, and generic readers may give it a different description.
How the DC-DC converter works
There is no alternator on an electric car. The DC-DC converter steps power down from the pack and keeps the 12 volt battery charged while the car is on or charging. The 12 volt battery wakes the control units, and the control units close the contactors that connect the pack. If the small side is not kept charged, the big side cannot help.
Common causes
- A fault in the DC-DC converter itself or its control
- A manufacturer specific fault, which some generic readers show under a different description
- Knock-on faults in other modules once the 12 volt side runs low, which then tend to show as U-codes
What to do now
- Write the code down, and have the car scanned for U-codes stored alongside it.
- Watch for the battery warning light. On an EV it points at the charging function the DC-DC converter provides.
- Have the 12 volt battery tested. It is cheap, and it is the most common reason an electric car will not start.
- If the car is slow to wake or the display is dim, book it in straight away.
- Do not open or disconnect anything on the high voltage side. Orange cabling is high voltage.
What people often get wrong
Thinking a new 12 volt battery or a jump start settles it. A jump start gets you moving but diagnoses nothing, and a battery that keeps needing one points at the charging system. Charging is exactly what P0A94 is about.
When the car must go to a workshop
Book it in soon. Diagnosing the DC-DC converter belongs with a dealer or a shop qualified for high voltage work, and EV diagnostics vary widely between manufacturers.
Read next
- The EV will not wake up: usually the small battery, not the big one
- P0A00 to P0A0F: motor, inverter and their cooling
- P0A80: traction battery degraded past the manufacturer's threshold
This page is general information and does not replace a professional assessment. Symbols, codes and behaviour vary between makes. Always check the handbook for your own car.
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