Power Management Unit

[Doncaster34]

I believe I am experiencing a malfunction with the Body Control Module (BCM) on my 2003 SL350. After replacing the batteries for the utilities, the central locking system malfunctioned after a mere 2 weeks, necessitating the use of the emergency key to open the boot. The newly installed battery initially displayed a voltage of 12.1 volts. However, after recharging it, the battery returned to its normal functioning state. The engine start battery is functioning properly without any issues. It seems to be a persistent issue with battery drainage or a malfunctioning BCM preventing the battery from charging. I have had a vehicle for a duration of 14 years without experiencing any issues related to battery depletion. Therefore, I assume that the Body Control Module (BCM) may be the cause of this problem. Can anybody provide advice or guidance on this matter?
1) Where is the BCM (Body Control Module) situated in the trunk and how can I access it?
2) How can I do a test for it?
3) It seems that fresh ones are no longer accessible. Is this statement accurate or does anybody possess knowledge of a reliable supplier?
4) Is there a service available for testing and rebuilding these units in case a new one is not available?
5) Any other recommendations for a solution would be welcomed. Using camper van split charge units as a substitute is an option that some individuals have considered, but it should only be considered as a last resort.

Thank you.

[BENZE220AMG]

Have you conducted a voltage measurement on the rear consumer battery using a Voltmeter while the vehicle is in operation?
The voltage reading should be within the range of 13 to 14.5 volts. Please ensure that the vehicle has been running for more than 5 minutes, since during this time the BCM directs power to the starting battery.
A code reader can detect and display any error in the Body Control Module (BCM).
If the automobile is not charging, potential causes include a malfunctioning alternator, a faulty battery, a stuck glovebox light leading to power depletion, or a malfunctioning BCM.
If the battery is low, the central locking system may not function.

An independent mechanic will diagnose error codes if you do not own an OBD code reader...

[KWILB]

One individual on either this platform or the other forum had an issue with the SL350 bcm. The item underwent repairs and the wiring was modified. Perform a search - the discussion was really illuminating.

Revision - I was active on a different online discussion platform. Post 366 in the thread titled "Living with an R230".

Edited August 29 by KWILB

[Doncaster34]

I will do a voltage assessment as recommended and determine the measurement. The battery is functioning well since it is just 3 weeks old. To troubleshoot the issue, I will remove the bulb from the glovebox light to eliminate it as a potential cause.

[Rudy7831]

This individual presents the problems to you.

[Rudy7831]

 

[KOOLCAR]

There is no need to remove any bulbs.
Activate the recording function on your phone's camera and see if the light ceases to emit illumination.

[Doncaster34]

Excellent idea!

[Doncaster34]

The battery was assessed after a 5-minute operation and is displaying a voltage of 14.1 volts. After following Ted's excellent advice, I examined the boot and glovebox lights and confirmed that both lights are turned off. I will attempt to connect a voltmeter in series to see whether there is any current consumption while all devices are turned off. Stay tuned for updates.