StephanZ

Constant problems with the trunk lock on my BMW 3 Series - What could be the cause?

Hello everyone, I have a recurring problem with the trunk lock on my BMW 3 Series. Despite several replacements, even with original parts, the lock keeps breaking. Most recently, it only worked for about 10 minutes before the opening mechanism was permanently activated and finally burned out. In recent months, there have also been other defects, such as the windshield washer pumps and the center console fuse. Since the last defect in the trunk lock, the OBD error message 009CB4 of the footwell module has also been displayed, but with a mileage that is far higher than the current one. Does anyone have any idea what could be causing these problems and how I can fix them without having to dismantle half the car? Many thanks in advance for your help.

(Translated from German)

The recurring trunk lock issues on the BMW 3 Series may be linked to a complex electrical problem, potentially involving the footwell module or the car's wiring. The OBD error code 009CB4 and other electrical defects suggest a deeper issue. Abnormal voltage readings, such as over 15V while running and 11.56V when off, indicate possible alternator or voltage regulator problems, which could affect the trunk lock and other components. A thorough check of the electrical system, including the battery, alternator, and voltage regulator, is recommended to identify and resolve the underlying cause.

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3 comment(s)

It sounds like you're dealing with a complex electrical issue. The OBD error code 009CB4 is related to the footwell module, which controls various electrical functions in your car, including the trunk lock. The recurring problems with different electrical components and the discrepancy in the mileage could indicate a problem with this module or the car's wiring. I would suggest starting with a thorough check of the car's electrical system, including the footwell module and the wiring. If you're not comfortable doing this yourself, it would be best to take your car to a professional mechanic. Please keep us updated on your progress. Do you have any other questions?

community_quotation:
community_author_wrote_on
It sounds like you're dealing with a complex electrical issue. The OBD error code 009CB4 is related to the footwell module, which controls various electrical functions in your car, including the trunk lock. The recurring problems with different electrical components and the discrepancy in the mileage could indicate a problem with this module or the car's wiring. I would suggest starting with a thorough check of the car's electrical system, including the footwell module and the wiring. If you're not comfortable doing this yourself, it would be best to take your car to a professional mechanic. Please keep us updated on your progress. Do you have any other questions?

Another observation I remember was during the last drive before the last trunk lock failed (was installed afterwards) that the board voltage displayed via Carly was consistently >15V. After the trunk lock failed, I left the car outside for several hours (at about 0°C) to drive it into the garage later. It started up reluctantly, and a short time later no longer started in the garage. The board voltage was only 11.56V (displayed via Carly), while the battery voltage was still 13.3V. Could these observations also have something to do with the problem?

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community_quotation:
community_author_wrote_on
Another observation I remember was during the last drive before the last trunk lock failed (was installed afterwards) that the board voltage displayed via Carly was consistently >15V. After the trunk lock failed, I left the car outside for several hours (at about 0°C) to drive it into the garage later. It started up reluctantly, and a short time later no longer started in the garage. The board voltage was only 11.56V (displayed via Carly), while the battery voltage was still 13.3V. Could these observations also have something to do with the problem?

Yes, these observations could indeed be related to your problem. The voltage readings you're getting are abnormal. A healthy car battery should read around 12.6 volts when the car is off, and between 13.7 to 14.7 volts when the car is running. The high voltage (>15V) could indicate a problem with the alternator overcharging the battery, while the low voltage (11.56V) could suggest a weak battery or a problem with the charging system. Both of these issues could affect the electrical components in your car, including the trunk lock. I would recommend having your battery and alternator tested. If they're both in good condition, then the problem might be with the voltage regulator, which is often part of the alternator but in some cars is a separate component or part of the ECU. Please keep us updated on your progress. Do you have any other questions?

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