Power problems and Power Module A158 error in BMW – how to solve it?

BMW driver question – vehicle wake-up and error A158

Power Module (Power Module) very often throws an error: A158 – battery disconnection (closed circuit current). After turning off the engine, the car is active for about an hour. This can be seen from the illumination on the side of the armrest of the seat panel. After this time, the power module cuts everything off.

When I open the driver’s door, I can not open the trunk lid, central locking from the inside. In addition, the side armrest panel is still not illuminated. Everything only activates when I press the ignition button or put the key in the ignition. Where and how to look for the cause of the popping error in the Power Module?

The problem occurred in the BMW 7 E66, but it may also occur in other models.

BM Cars service response – causes of power problems in BMWs

The described problem is more complex and affects not only the Power Module. A BMW car should “go to sleep” after turning off the ignition and closing all the doors within a maximum of 20-30 minutes. This time depends on the model and the number of controllers – that is, additional equipment on the vehicle.

In the case of the E65/E66 model, the additional equipment is very rich. Therefore, the sleep period may be a little longer, but certainly should not last about an hour. Once the vehicle is asleep, the resting current consumption should drop to 0.05 A. In this position, the vehicle can park for an extended period of time without excessively discharging the battery.

Any agitation of the vehicle especially related to the opening of the driver’s door excites the vehicle preparing to start the engine. The interior lighting should be started, in addition, the fuel pump gives an initial dose of fuel to the engine. Current consumption then increases to several Amps. In this position, the vehicle is ready to start the engine and drive.

In the described case, the correct transition of the vehicle to sleep is not seen. In addition, after an hour has elapsed and the vehicle is asleep, there is no excitation of the controls when the driver’s door is opened. This behavior of the vehicle may indicate not only a failure of the Power Module, but also a problem with another controller or controllers that cause the vehicle to wake up and sleep for too long.

It could also be due to communication problems between the controllers or a lack of proper power supply to any of them. To solve the above problem and make an accurate diagnosis, we suggest the following plan of action:

1. Full diagnostics of the vehicle with special attention to the errors of the controllers and communication between them.
2. Measurement of the state of the battery and charging.
3. Measurement of resting current consumption.
4. Disconnecting more controllers from the CAN bus and fiber optic cable to find the cause of increased current draws.
5. Oscilloscope measurement of the state of the CAN bus.

We can perform all the above activities in our service center by appointment.

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