Fix BMW fault "increased battery discharge"

We discussed “high rate of battery discharge” in the post four days ago, and we will share a similar fault “increased battery discharge” in this post. Also a real case, check following:

Vehicle information

Model: BMW X5

Year: 2012

Engine: N55

 

Fault symptom

Message “increased battery discharge” appeared in screen many times, and the engine start time is longer than before.

 

Possible causes

1. Bad battery

2. The excessive standby current of the vehicle causes the battery power consumption;

3. The installation of electrical appliances in vehicles leads to excessive power consumption.

 

Fix process

1. Got fault code “387F – Power management: standby current violation” after diagnose scanning.

2. Perform power diagnostics to detect vehicle standby: excessive standby current!

3. After analyzing the data, it indicates that the sleep current has been faulty in recent time, next step is detect standby current.

4. First test the battery. Use a battery tester to check that the battery power is 88% and the battery is normal.

5. After calibrating with a 100A current clamp, clamp on the battery negative wire. The computer executes the PowerDown command to put the vehicle into forced standby.

Soon the car entered the standby state within 1 minute, and the minimum standby current measured at this time was 176mA, indicating that there was a current leakage in some places.

6. In order to find out which power supply line is leaking, we use a current clamp to measure the positive power supply line one by one. When a power supply line is measured, the current is 175 mA, and the other lines are about 1 mA. It is this line that has a leakage current. Next, we look for the circuit diagram. Unfortunately! We didn't find out what part this line was for, we had to find it by ourselves.

Power-management-standby-current-violation

7. Following the line, we found that the power was supplied to the rear power distribution box.

fix-fault-code-387F

8. At the power distribution box, we need to find the leakage point. We unplug the electrical plug on the power distribution box to find the electrical appliances. After removing the plug as shown in the photo, the standby current is normal!

9. It is also normal to unplug the F174 fuse on the power distribution box. It is found that the fuse is supplying power to the audio case.

possible-causes-of-increased-battery-discharge

10. After disassembling the audio case, it is found that there is an installation of electrical appliance, and the standby current is become to be normal after removing this electrical appliance.

 

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