B11DB-87 Battery Monitoring Module Fault

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Edgyver

Member
Joined
Sep 23, 2021
Posts
10
Reaction score
2
Location
Texas
I'm having a charging issue with my 2011 LR4. I got a battery light and not charging message while driving. I hooked up my Gap tool and found that at idle the alternator load was 100% with minimal accessories on. After checking the basics, I replaced the alternator and battery with an OEM Denso and Odyssey AGM.

I reset the battery in service life and initially everything worked great. The same alternator load reading at idle dropped down to 23% from 100 but after a couple of test drives the voltage reading dropped down to battery voltage. This time without any warnings on the I-Pack. After checking I found in the BCM, fault code B11DB-87 Battery Monitoring Module - Bus Signal/messsage failure. Anyone have experience with this fault?
 

Rover Range

Full Access Member
Joined
Jun 13, 2022
Posts
534
Reaction score
290
Location
Texas
Land Rover has a TSB to address this DTC. LTB00643

There's a fuse link that attaches to the battery positive battery terminal for the battery monitoring system.
It is a single wire. You can tug on it and see if it pulls apart.
If it does, you will need a new fused link lead.
Part # LR057241
 
Last edited:

Edgyver

Member
Joined
Sep 23, 2021
Posts
10
Reaction score
2
Location
Texas
Yes, I found that bulletin and will do it this weekend and post the hopefully successful results. My concern is the intermittent nature of the charging. A fusible should either be open or closed. Not usually operable intermittently. Thanks!
 

Rover Range

Full Access Member
Joined
Jun 13, 2022
Posts
534
Reaction score
290
Location
Texas
There's going to be a programmed delay in the battery monitoring system turning the light on. Otherwise, the warning light will be flashing on and off with every voltage change.
 

Edgyver

Member
Joined
Sep 23, 2021
Posts
10
Reaction score
2
Location
Texas
Okay, yeah, that's makes sense. One more question, what is the device on the negative battery terminal and what's its purpose? Will it create a charging issue as well? Mine looks "okay" but is a little discolored. Don't know if that means anything.
 

Rover Range

Full Access Member
Joined
Jun 13, 2022
Posts
534
Reaction score
290
Location
Texas
That is part of the Battery Monitoring system. Sends the battery voltage signal back to the body module.
 

Edgyver

Member
Joined
Sep 23, 2021
Posts
10
Reaction score
2
Location
Texas
Well, here's a hopeful wrap up to this story. I cut out the fusible link (blue/brown) wire to the + battery post and replaced it with an inline 5A fuse but I still have the same issue. No difference made, so I turned my attention back to the alternator. After trying two Denso alternators I installed an OE Land Rover alternator and the issue seems to be fixed. Every now and then the charging system voltage while driving will briefly drop down to battery voltage, around 12.2-12.6 but this does not cause any issues. It seems the BMS is requesting no voltage from the alternator due to it's fuel management strategy of reducing load on the engine when able to. Most of the time voltage remains in the 13.0 - 14.2 range while driving. Something to note, when I replaced the alternator I installed an Odyssey H8 battery and this could of led me to get peculiar voltage readings. These vehicles came with a lead acid battery which the BMS was programmed to control. So I don't really know how much my AGM battery effected that programmed strategy but everything seems to be happy now.

I hope this helps you get your repair done quicker with better understanding of how this overcomplicated system operates. Cheers
 
Last edited:

Latest posts

Members online

Forum statistics

Threads
36,222
Posts
217,569
Members
30,473
Latest member
OnoA
Top