Head Unit stopped working

[Slowpoke13]

2012 LR4 115k

Head unit goes dark when I put in reverse and does not have backup warning. Will not pair phone, cameras inop, radio intermittent Sat radio inop (always searching).

Received “U1A24-87 (2F) MOST Ring complete, no communication - Bus signal/message failure - missing a message” on the AAM (audio amp), ACM (audio system), FCDIM (front control), SRM (satellite radio), & TEL (cell phone) modules.

I can associate all the fault signals to the various symptoms. Assume it means the head unit is toast. Correct? Would it be any other component? Any suggested replacements other than OEM? Would one of the Yates “Tesla style” replacements be a good option (does he still make them?)?

 

[itsaguything]

What are “all” the codes being thrown please.

 

[Longtrail]

FWIW I had head unit issues when I first purchased my used LR4, it wouldn't remember radio history from one start to the next. I found a replacement unit on Ebay (being very careful to find the right model #), once installed I've not looked back...

 

[Slowpoke13]

What are “all” the codes being thrown please.

Those are all the codes.

Does anybody have a MOST diagram? And, any preferred fiber jumpers for trying to isolate where the failure is?

 

[itsaguything]

I would start with the easy path first (as described in the workshop manual)
1 verify the battery reads 12.6 v (when engine not running of course.
2 perform a reset. Disconnect battery wait 60 mins (or touch neg, pos leads together to dissipate capacitance)
3 reconnect the leads to the battery
4 press start button w/o touching brake
5 wait for dings, chimes, whirs to stop
6 start engine
7 check codes.

Then if needed, check each component…
I’m assuming of course that all fibre for the MOST network is suitably attached tightly.