So the wife went to work and said the turn signals stopped working. Right and left. I go check it out to find signals not working but flashers were. No sound but they would flash. The first disturbing part was I couldn't find a fuse to check. Couldn't find it in RAVE either. So we switched cars. On the way home I tried the left signal. Nothing then 10 seconds later, with the switch off, it comes on and wouldn't shut off. Then it did. Same with the flashers. Then the seatbelt warning came on. Then off. Then the Air suspension inactive warning. Then off. Finally I noticed the infotainment screen was off and the system wouldn't come on. A few months ago I did the $7 amp bypass on the BM54 and fixed it. Lots of hum from poor grounding but at least I could change my settings.
I first suspected water in the system due to monsoon like rain for 4 days but everything in the boot was dry. I pulled the stereo fuse for fear of another battery drain and rechecked the signals and hazards. Both back to normal.
Anyone know if a screwy BM54 can cause havoc elsewhere in the electronics? Thanks

Last edited by doclees on 25th Jul 2018 3:31pm. Edited 1 time in total

I had this intermittently and could not find a solution.

However, quite separately, in resolving a battery drain I took the satnav unit apart to find corrosion on the PCB, cleaned this up and battery drain gone. All the stuff in the boot is more or less somehow on the same fuses/circuit - Satnav/Radio/On Board Computer etc.

Might be worth a look see  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Thanks. I spoke too soon that pulling the infotainment fuse gave me back signals and proper hazards. Went to run to the store and they are still not correct. So maybe bad relay? Back to the wiring diagram.

I'm believing the problem may be in the LCM. RAVE says needing Testbook 4 to reconfigure a new one. Are these vehicle specific or can I swap in another one from a 2004?

OK this all may be a big "never mind". In pulling LCM to look for corrosion I first disconnected the battery ground. Well it pretty much came off on its own. For completeness sake I pulled the LCM and found no corrosion on pins or board. I added a couple of lock washers to the ground clamp. At this moment the problem is solved.
I still would like to know if in the future if the LCM is replaced will it need a Testbook 4 reset.

Some have just been able to replace the LCM without problems (2nd hand) whilst others indicate some recoding is required (possibly new ones ?)

Search the forum for a haystack of results on the "LCM" .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

"I first disconnected the battery ground. Well it pretty much came off on its own."

Could that have been the cause of the problem? ie. intermittent current drops. John
2008 Stornoway Grey 3.6 Tdv8 Vogue
2005 TD6 Java Black Vogue - Written off!!
GAP iiD BT
2003 Discovery TD5 Auto, Nanocom Evolution - gone to a new home!
MasseyFerguson 152 - No electronics!! - Sold

Yes seems to be. Looks like it killed my infotainment screen. Time for an Android unit.

I replaced my LCM with a secondhand one and it worked perfectly without any re-coding required.

Only thing that altered is a "dot" in front of the recorded mileage which shows that a part has been changed.

The LCM contains the about 1/3 of all the vehicles configuration, if the doner vehicle is of the same spec and has the sam factory options fitted/enabled then it will work. However you may find that the doner vehicle had different options fitted/enabled and some systems may no longer work on your car until it is recoded.

The tamper dot on the instrument cluster means that the millage in the instrument cluster, EWS and the LCM do not match.

Matt Current
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Thanks folks, I may be back to swapping one out. Wife just texted the signals not working again. My iidtool has shown low voltage errors for the headlights since I purchased both RR and tool about 50k miles ago. This is why I was looking at the LCM. Maybe the loose ground cable was just coincidental.
Any way to test if the LCM is defective? Would a Testbook 4 evaluation find it?

Current update is that signals worked fine on way home wife says but added she didn't have lights and A/C going so less electrical stress. I'll try it later with lights wipers AC and radio.

Update: do the following faults point to LCM errors? 0x2A headlight (RL) ignition voltage <7 5 volts, 0x88 I-Bus fault, 0xBE Lightning Control Module error, LCM-Light Control v11, 0xC ECU EEPROM fault. I don't remember the lighting control faults being there in the past.

Try clearing the faults then (does this fix anything?)

1. See what comes back immediately
2. in a few days .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

At this moment all is good. I took it out with lights/wipers /AC/hazards /radio. No issues. Checked live battery voltage -13.9. I will go clear them. I know the list was holding the left signal bulb out fault. I replaced the bulb just before this all started. Hmmmmm.