P0A94 on BMW: How to Diagnose & Fix
DC/DC Converter Performance
1 BMW model · 1 documented issue · 1 critical
P0A94 on BMW by model: symptoms, diagnosis and fix
NHTSA campaign 23V449000 recalls BMW iX, i4 and i7 vehicles whose Combined Charging Unit was not manufactured correctly, leaving internal components improperly connected or assembled. The important distinction for iX owners is the failure mode: this campaign is not about AC charging refusing to work, it is about the CCU interrupting electrical power while the vehicle is in motion. NHTSA records the consequence as an improperly assembled CCU that 'can interrupt power and cause engine stall, increasing the risk of a crash.' On the iX the CCU is the combined on-board charger and DC/DC converter, so a fault there simultaneously threatens both traction power and the 12V supply that runs steering assist, brake assist and lighting. This is consistent with the 2023 iX complaint file, which contains multiple reports of losing propulsion and, in the worst cases, of losing power-assisted steering and braking together at speed - one complainant describing that they 'lost power assisted steering AND power assisted braking. I had to decelerate with no power brakes.' The remedy is replacement of the CCU, not a software update.
How to Fix
Check your VIN against campaign 23V449000; the remedy is free replacement of the Combined Charging Unit by a BMW dealer. Because a CCU fault can take out both traction power and 12V accessory supply, do not defer this recall and do not treat a single unexplained power interruption as a one-off - have the dealer pull the CCU and EME fault memory for DC/DC converter and internal-communication entries. If the car has ever dropped both power steering and power brake assist at the same time, report it to NHTSA as well as to the dealer, since that combination is the signature of a supply-side rather than drivetrain fault. Out of warranty, CCU replacement on the iX typically runs $2,500-$5,000 including programming; under recall it is free.
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Sources for this issue (2)
P0A94 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0A94 mean on a BMW?
P0A94 stands for "DC/DC Converter Performance." This hybrid/electric vehicle code sets when the hybrid control system detects that the DC/DC converter is not performing within expected parameters. The DC/DC converter steps the high-voltage battery power down to the 12-volt level that runs the car's lights, accessories, and control modules, so a performance fault can affect the whole low-voltage system. Symptoms may include warning lights, reduced power, the hybrid system not starting, or a discharged 12-volt battery. Because high-voltage components are involved, diagnosis and repair should be done by a qualified hybrid technician. On BMW it is documented across 1 model: iX.
What are the most common causes of P0A94?
The most common causes of P0A94 are: Faulty inverter/converter assembly (DC/DC converter), Open or shorted wiring in the converter circuit, Poor electrical connection at the converter, Weak or failing 12-volt battery, High-voltage system or cooling fault affecting the converter, Software/control module calibration issue, Faulty hybrid control module (less common). The specific cause varies by vehicle.
How much does it cost to fix P0A94 on a BMW?
Repair costs vary widely with the root cause and BMW model; each issue on this page carries its own estimate where one is published.
Looking for P0A94 on a different make?
View P0A94 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.