Righto - long story but here goes..
pour a cuppa and read on...

New 2019 CX5 Maxx sport.. Parked in Freo and some low-life hit it while at work.. (right rear wheel arch(rear side of plastic trim))
Sorta mangled the arch trim and poked a hole in rear bumper just where trim meets bumper.. musta been a pole out the back of a ute or something?
anyway.. a new edging (trim) covered 99% of the damage, glued some plastic behind the 5mm hole on bumper edge, and filled it flat.. bit of touchup paint and very nearly perfect.. didn't need to remove bumper to repair.. just inner guard splash cowling, to get to the spot...good enough anyway.
2 years later, another low life dents the left front door.. very small, but a ding right in the middle.. just a 1cm door jar.. got a panel beater to repair/respray - looks perfect..
however.. driving home - "BSM Malfunction" is on the dash.. !! turned around and took straight back.. Painter said might need computer resetting after being disconnected? took it to an auto guy up the street, but brought it back 30 mins later and said he tried but won't clear the message, might have to get Mazda to do it... Swears that all was re-connected in door.. Kinda believe him.
Just so happens, rear left seat belt stopped retracting a month earlier.. rang Mazda.. brought it in to be inspected.. covered under wty but gunna be 4 months for a replacement seat belt to arrive..
back to today....
So.... I ring Mazda, tell em the BSM Malfunction is appearing on dash and could it be looked at when the belt is fixed.. yep, yep..
4 months later, get a msg the belt is here.. also due for a service so booked it in, and confirmed with them to look at belt and BSM issue at the same time.. sure sir...
Pick the car up.. service done.. but sorry belt is not here, will have to bring back .. grrr.. (but not a biggie) ALSO.. we didn't touch the BSM Malfunction issue, as we saw there has been a repair on the rear right bumper.. and to diagnose the BSM we'll have to remove bumper, test sensors, and re-install bumper ($900) and if we find the BSM issue is a result of the impact to bumper, then not covered under wty (so $900 + cost of BSM repair??) more Grrr..
And... that would be fine.. should that be the case, however.. impact was 2 years earlier.. was a good 9 inches away from the BSM sensor unit (which is not attached to bumper.. it's bolted to chassis)
........and it happened at same time painter worked on front door! ??
The icon on the dash shows a car with the radar lines to an object on right rear..
Q: is that just a generic error icon.. or does it mean the actual RIGHT REAR BSM sensor is the cause of the issue? (like if the left sensor was at fault.. would it display the object to the left of the car symbol)
Q2: The timing of the painter touching the left front door/mirror? is just too coincidental.. Can the mirror/door be the cause of the error (noting that BSM only has 2 REAR corner sensors, I think the mirrors just display the relevant viewable warning indicators when a car is present in each respective blind spot)When I first turn the car on by pressing push start button, on my right hand side mirror I get the BSM symbol for a second before it disappears (which is meant to happen according to my Mazda manual for the car) This symbol is meant to come up on both mirrors when turning car on for a split second then disappear but it's only doing it on right side mirror & not the left mirror.

When locking & unlocking my car I get the BSM symbol appear only on my left hand mirror (which I believe this should not occur when locking & unlocking my car ..Mazda manual doesn't say this)

When you pass a car driving on either side of the car the BSM symbol should appear to warn you of a car in your blind spot (neither mirrors get the BSM symbol when this happens)

When I am driving or stationary & I put my left hand indicator on it flashes the BSM symbol on the left mirror. This is only meant to happen when something is in your blind spot & indicator on but it's happening when nothing is in my blind spot. Everytime I indicate on my left I get the BSM symbol flashing on left hand side mirror & this does not happen at all on the right hand side mirror indicating to the right.
hmm.. left mirror BSM indicator lights-up.. (hence harness in the door is connected/plugged in fine..etc..)
So... With all this above, anyone know what the cause would be?
I would have thought the Mazda dealer could check the operation of the 2 sensors without removing the bumper, and just read the diagnostic codes/results... right!
they should also have a doppler unit I should expect?
Anyway, I recon they will get the car, say it's the rear right sensor (regardless of what the issue is) and justified by the repair, proceed to charge full amount.. money for jam.
Might just have to bend over, but thought I'd ask first..

Thanks for persisting this far,
Any thoughts?
AJ

 

There appears to be something going on with the wiring in the LHF door or mirror. Something has connected the indicator with the BSM wiring to the mirror glass.

There's nothing stopping them from connecting MMDS ( Mazda's scan tool ) & reading fault codes.

 

Thanks for the quick reply Grim_reaper..

Yeah, the respray of LHF door and timing is just waaay to coincidental eh..

I will remove the LHF door card and mirror this weekend and check what I can.. maybe he crimped a wire?
will re-seat all connectors etc..
whether removing the issue clears the error immediately.. or whether the code needs to be manually cleared/reset after resolution??
hope the former..
Yeah... I would have thought the least they could do is pinpoint the actual cause via their diagnostics eh... They had it there all day!.. guess they just want to leave it ambiguous till then.
Will advise how it goes...
thanks again..
AJ

 

Well done Grim-Reaper..
I pulled the door apart, mirror off.. checked it all out..
A: the flashing of the BSM indicator when left indicator is on... noticed this was substantially dimmer than the RHS mirror BSM symbol (that shows for 1 sec with engine start)
pulling mirror off and messing with it.. looks like the actual flasher light on end of mirror housing was bleeding the light back behind the mirror to make it look like it was flashing.. from driver angle.. so that stopped flashing when re-assembled..?
still no BSM indicator showing on engine start on left mirror..
inspected the little 9 -ish pin connector for the mirror harness.. 1 pin bent...!! straightened that and re-connected (carefully) woof.. BSM indicator comes on for 1 sec just like RHD with engine start..
so.. the issue introduced by paint dude is now resolved... (pretty conclusive.. glad to find a solid cause.. hate random stuff)
however..
Still get BSM Malfunction on dash with engine running...
Q: now that the condition that initially (and persistent till now) has been corrected.... What is needed to reset the BSM Malfunction status...
almost 100% sure it has nothing to do with the deal on the rear bumper (99.97%).. as per my reasoning above..
tried removing battery lead for 20 mins.. same deal but..
If you goto console screen and try to turn off BSM, it un-ticks then re-ticks itself automatically after 1 second.. guess they won't let you.. safety and all that..
tried my ODBII bluetooth unit, reset all codes.. it went through & cleared like 39 codes .. but guessing BSM wasn't one of them. still there.
Might give the painter a ring, tell him we found 'his introduced fault', see if he'll take it to his mechanic mate - re-try resetting with his kit.. might work now that the cause is corrected?
If no good..
Might take it to a different Mazda dealer and ask them to try a computer reset with their Mazda specific diag kit...
Would like to know if a CX5 should reset the condition automatically once the issue is no longer present, or if it needs intervention to be cleared..
if it is supposed to clear automatically - then there must be an issue still.. if it needs a manual reset - could be sorted.... and just bad programming by Mazda eh!
Anyway, will post back after I can get it reset.. here's hopeing..
AJ

 

Thought I'd complete the post..
So .. After correcting the bent pin in the mirror connector, took the CX5 back to painter, who took it to his auto electrician.. it would reset but come back on next start..
I didn't trust the first Mazda dealer, just seemed like they were going to try to void warranty no matter what..
So took it to another dealer, they said 'yep.. drop it off and we'll take a looksee'
dropped it in, they said diags point to LHS fault and to fix it, would have to be left for a couple of days..
(well.. at least they can't blame the rear bumper scratch, as it was RHS)
left for 2 days, they said they replaced the module in the left mirror and full tests fine!.. and it's covered by wty.. nothing to pay.
picked it up this arvo, all good.
I think (just thinking out loud here), they reset.. error disappeared.. couldn't find a fault, but procedure is that they have to do FULL testing on safety functions?
so replaced mirror module to be sure..

anyway..
all sorted.
on one hand, being a safety 'thing'... I can see why they might not let it 'sort' itself... but it should be capable of testing during start, and reset the error if it consistently passes..
AJ