Convertible models of the BMW E-Series and Mini R-Series generations are equipped with a module that protects the occupants during a “rollover” crash.
These modules can fail after disconnecting the battery or if the battery is discharged too deeply. There are also other known cases where the controller spontaneously malfunctions.
You can recognize the fault by the following error codes and an error on the dashboard:
- 9402 Internal error
- 9402 Rollover-protection controller: internal fault
Relevant part numbers:
- 9264926
- 9201128
- 9187933
- 9180627
- 9179400
- 9134734
- 6950640
- And more
The ROC is present in, among others:
- BMW 1 serie – E88
- BMW 3 serie – E93
- BMW 6 serie – E64
- Mini R-serie

What does the rollover controller do?
The rollover controller is part of the BMW and Mini’s safety system. The module is designed to protect occupants in the event of a rollover crash, i.e., if the car rolls over or is about to roll over. The rollover controller is a computer that uses sensors to measure the car’s motion and determine when a rollover is imminent. These include gyroscopes, which measure motion along the horizontal and vertical axes, and accelerometers, which measure the car’s acceleration.
If the rollover controller detects a rollover, several safety measures are activated. The exact measures depend on the sensors. For example, the seatbelts are tightened and the side and curtain airbags are deployed to protect the occupants from injury. The fuel system can also be deactivated to prevent a fire in the event of an impact.
The rollover controller is an important part of a BMW’s safety system and contributes to the protection of the occupants in the event of a rollover.
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Fault
Unfortunately, the ROC module sometimes fails. In that case, a fault will be visible on the dashboard or via the iDrive. You can also recognize the ROC fault by the following error code in the airbag module (ABG/ACSM): 9402 Rollover-protection controller: internal fault.
This error often occurs when the battery has been discharged or due to a voltage spike in the car’s onboard electrical system. This can corrupt the data on the chip (EEPROM). The computer then detects this error and displays an error code.
It’s important to have this checked as soon as possible. Otherwise, a rollover crash could be fatal!
References
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There are two ways to resolve this issue. First, the module can be replaced with a new one, which is the most expensive solution. Fortunately, it’s also possible to repair the module.
During the repair, the chip is read, the data is recovered, and then the chip is rewritten. This is done using specialized programming equipment. After this, the module will function normally again. There’s always a very small chance that the module actually has a hardware defect; in that case, the memory may become corrupted again after the repair. Normally, the problem is permanently resolved.
Note!
Unfortunately, there are also companies that can (cheaply) write off this error. This is extremely dangerous; absolutely do not try this!

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