Tinkering with a cheap 2008 LR2 I picked up. It had a dead battery and seems to be in crash mode with all the standard codes (E on dash, hdc and transmission error and permanent crash mode errors in the system). Most electrical systems seem to be working except for the headlights that I can't turn off.

Tried to do a crash mode reset with SDD but I can not seem to clear it. Is it a sign of a bad BCM?

One additional weird thing is that when testing I get an notification that the measured voltage is 36.3V instead of an expected 12V .. presumably a possible bad voltage regulator? Am a little bit stumped at the moment and would love to see if anyone has some tips..

Replace the battery with a good fully charged one. Run a fault code reader. Do all alternator tests particularly AC ripple.

Battery is a known fully charged one that's good. Since it's in crash mode I dont get the crank to test the alternator voltage.

The battery it came with, whilst only 3 months old, has been depleted and got a bad cell so its junk.

This error is throwing me off though but my hunch it is a clue to what is going on.

I assume the battery voltage is actually normal when read with a multimeter. Have you a different code reader to try out

Could you add the vehicle details to your profile please

Crash status has likely been set because the battery voltage dropped below 8.5V while the ignition was on. I had the same issue on mine when I first got it.
SDD should clear it no problem, although I used my IID to clear mine.
Definitely replace the battery with a fully charged good quality higher capacity 110 instead of the standard 096 size.
These vehicles are very heavy on batteries, as voltage fluctuations when starting cause all sorts of odd issues.

The battery voltage reading error is strange though, but I'd not be overly concerned. 2009 Rimini Red SE TD4. Soon to be sold.
Hyundai Ioniq 5 Ultimate on order.
Gone. 2006 Tonga Green i6 HSE.

I Like Chips wrote:

I assume the battery voltage is actually normal when read with a multimeter. Have you a different code reader to try out

Looks like resetting the crash mode is the least of your worries. Is there anywhere near you that can check/reset/rebuild the ecu. As a basic start. I assume you have gone over the wiring

I was able to reset my crash codes with SDD when I bought my vehicle used. My codes were likely due to a dead battery. It would appear your codes are related to an actual crash and the ECU might be the issue as mentioned. Might need a new ECU programmed.

Wiring actually does not look bad at all. I cleaned the connectors on the main bcu junction box as a start. I am approaching this as a challenge though.

I have some repairshops nearby but not sure if they can reprogram/rewrite the main bcu. There is a company in NY that says they can do it for about 300 dollars. I am getting signal on the can high and low bus from the odb2 plug so there is some.comms going out from the main bcu.

I wonder if unplugging each of the non responding control units, from the above pic. and rerunning the test might show a different result (assuming maybe one of them is bad).

The one that seems weird is a non responding headlight switch though.

Left the car alone for a few days and tried a few things today. Got a few additional modules back in green that were not before. Still not getting the abs/atcm/rcm to respond but I am wondering why the tcm is listed as not present. I want to check the connector of it and see if it is corroded/dirty since there is some oil there. What is the easiest way to get to it?

Click image to enlarge

The TCM sits on top of the auto box, you can easily see the cable and connector at least on the diesel version. If you have checked out the circuits, connectors for anything loose or corroded and I would go back to basics myself starting by having the ecu checked out. Is it possible to remove some of the module connectors to pull them out of the equation.

You need to test the CAN BUS physical layer, see Alex's note in this thread
https://www.freel2.com/forum/topic32050.html?highlight=bus

Have you searched Forum for CAN BUS Related info
https://www.freel2.com/forum/search.php?se...rch_time=0

https://www.freel2.com/forum/search.php?se...rch_time=0

Googling CAN BUS TESTING will give you helpful clues on how to do it.
https://www.google.co.uk/search?q=CAN+BUS+...nt=gws-wiz

Once you know the Physical Layer is OK, then you can then start checking the individual Modules (and their inputting sensors) FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 76k+ miles) (MY2015)