BMW owners may occasionally see a drivetrain warning linked to the EME high-voltage starter generator. Two messages can appear:
- Yellow warning CC-570: Continue driving in electric mode. Drive system malfunction.
- Red warning CC-173: Restart not possible. Drive system malfunction.
The related diagnostic code may appear as 0x03907F – Control unit: internal error, which usually points to a software-related issue inside the EME control system.
In the worst case, the high-voltage starter generator may not restart the combustion engine during the current driving cycle. That sounds serious—and seeing a red warning on the dashboard is never fun—but the cause may be an unfavorable software application rather than a failed mechanical component.
The First Step: Perform a Terminal Change
A BMW technician may begin by carrying out a terminal change, which is essentially a controlled vehicle power-cycle procedure.
After the terminal change, check whether the combustion engine starts normally. If the engine still refuses to start, the next step is to place the vehicle into sleep mode.
How to Put the BMW Into Sleep Mode
Follow these steps in a safe location:
- Park the vehicle securely.
- Switch the vehicle off.
- Lock the car.
- Move at least 10 metres away from the vehicle.
- Wait approximately 10 minutes.
- Return to the vehicle and try again.
This allows the vehicle control units to shut down fully and restart cleanly. In some cases, the warning clears and the journey can continue without further action.
BMW’s Remote Software Upgrade system can deliver software improvements and stability updates through the vehicle or the My BMW App, although availability depends on the vehicle, equipment and market. (BMWUSA)
Is an ISTA Diagnostic Check Required?
According to the service procedure supplied for this fault, an ISTA diagnostic check is not required immediately if the vehicle responds to the terminal change and sleep-mode procedure.
If a customer reports the warning, the process can be applied straight away. However, if the warning returns, the engine will not restart, or the vehicle becomes difficult to move, professional diagnosis is the sensible next move. High-voltage hybrid systems are not suitable for DIY repairs.
Install the Recommended Software Upgrade
The long-term solution is a Remote Software Upgrade performed by the vehicle owner, where supported.
The relevant software target is:
I-level 25-07-551 or higher
The update became available from September 2025, but release timing and compatibility vary by market and vehicle specification. BMW confirms that eligible vehicles can receive software updates through the My BMW App or directly through the vehicle’s built-in connection. (BMW)
Before starting an upgrade:
- Park the vehicle safely.
- Make sure the vehicle has sufficient battery charge.
- Do not use the car during installation.
- Follow every instruction shown on the central display.
- Allow around 20 minutes for installation after the software has downloaded.
BMW notes that Remote Software Upgrade availability depends on the vehicle’s hardware, operating system and market. (BMWUSA)
When Should You Visit a BMW Specialist?
Arrange professional assistance if:
- The engine still will not restart after sleep mode.
- The red drivetrain warning remains active.
- The vehicle enters a restricted driving mode.
- The fault returns after the software update.
- Additional high-voltage or battery warnings appear.
Do not open or disconnect high-voltage components yourself. The EME system operates with dangerous electrical voltage, and repairs should only be carried out by trained BMW technicians.