Cargo Light not working

Kedis82ZE8

'15 CX-5 AWD GT w/Tech Pkg
Contributor
So many misc thread so wasn't sure about resurrecting an old one.

Anyway.... notice the cargo light was working. I put in a VLED a year or so back and it has worked fine. I can't remember when it stopped working.

I put in stock good bulb and no go. It seems there is a ground or voltage issue.

Can the RBCM be damaged? and if so would it only affect the cargo light? I tested every light and function in back and the cargo light is the only thing that doesn't work.

I still have a few thousand left on 3/36 so will let dealer deal with it. I left stock bulb in there in case I need to take to dealer.
 
Lift Gate Latch Switch works.... or I assume that is the exterior button and not some microswitch in the actual latch assembly?

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.... notice the cargo light was working. I put in a VLED a year or so back and it has worked fine. I can't remember when it stopped working.

I put in stock good bulb and no go. It seems there is a ground or voltage issue.

Can the RBCM be damaged? and if so would it only affect the cargo light? I tested every light and function in back and the cargo light is the only thing that doesn't work.
I believe you forgot to turn on the switch which is located next to the cargo light. :)

Seriously, RBCM can get damaged for pre '15 CX-5 as the cargo light somehow isn't fused. The worse case scenario is your VLED had shorted it out by itself, hence burned the RBCM. Have you physically measured the voltage of bulb sockets and can you see 12V when the cargo light is supposed to be on? Can you verify the VLED you used for cargo light is working by testing it on the map/dome light (measure the ohms first and make sure it's not totally shorted, i.e. 0Ω)? I guess the best is to let dealer handle it as the module is expensive. if indeed your RBCM got damaged, you may consider add an inline fuse if you plan to use an LED again.
 
I'll do a voltage test this week. It's not totally shorted... not sure what expected Ω rating of LED bulb is. I'll have to look at that. Not shorted.... if this did cause issues gonna stick purely with incandescent in that area. I've got another fused LED bulb in the 12V adapter in rear that puts out enough light. I did the little screwdriver trick in diagram above but still could get door lock to release. Had a brief panic and then popped off that inside cover. The white plastic piece below is a release for the mechanism.

IMG_6665.JPG



Of course in the grand scheme of things I can think of far worse things to be out that the cargo light.


EDIT: LED bulb is coming in at 300Ω
 
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Did you disconnect the battery before changing? There are specific warnings in the service manual to do this otherwise the RBCM could very well be damaged.
 
No, I just disconnected light assembly & swapped bulb two years ago and haven't touched it since. If damaged it certainly took its time to fail.. probably a cold solder joint or bad ground. I think now it seemed to happen after sitting out in the near zero cold for a week or so.

From what I have read it seems most who damaged RBCM tried changing the bulb in the assembly while still connected. In FSM that just looks like standard warning of working with electrical & disconnect to be safe. I suppose if someone got sloppy with a screwdriver extracting light assembly they could short something out.

Bulb was also perfectly seated in socket when I extracted so no short happened there. Might just be a red herring that I put in the LED years back and module failed or it isn't the module either. It was under a lot of snow and ice... maybe there was some intrusion somewhere in the lock mechanism? I'll probably take it in a few weeks from now.

I don't mind them messing with those panels... I don't like dealer touching passenger doors though.

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It's not the separate latch microswitch as dashboard door indicator shows hatch open & closed. Looking closer at how this thing is wired it does appear to go directly to the RBCM. Lots of troubleshooting data in manual but of course need a M-MDS to interface with it. Even if one got the module it appears you need Mazda dealer to program it according to FSM.

Looking at the TSB it mentions that disconnecting the cargo light connector is acceptable as well when swapping bulbs.

EDIT: Looking around part number appears to be KD45675Y0G and can be obtained for around $120-$135
 
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Burnt module due to short because battery was not disconnected.
 
Burnt module due to short because battery was not disconnected.

I don't disagree module is now impaired...maybe a bad solder joint but as you can see from TSB battery disconnect is "not required". I did the latter and has been fine for over 2 years.

EDIT: I should say... not the only method as it is a viable option as well.

http://am.mazdaserviceinfo.com/mazdaesi/index?page=detail_pagelet&id=TSB1347

"TO AVOID DAMAGING THE RBCM DURING CARGO COMPARTMENT LIGHT BULB REPLACEMENT, ALWAYS DISCONNECT THE NEGATIVE BATTERY CABLE OR THE CARGO LIGHT CONNECTOR."

It is easy to see this switch and how it is wired isn't the greatest work of engineering. If one did leave connected it would be relatively easy to create a short.
 
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When I swapped my bulb for an LED, I just disconnected the switch first. Never had any problems.
 
Burnt module due to short because battery was not disconnected.
No you don't need to disconnect negative on battery while replacing the cargo light if you know what you're doing like Kedis82ZE8 did. He disconnected a connector to the cargo light, which has the same effect as disconnecting the battery. Kedis82ZE8's RBCM may be bad right now but definitely is not caused by improper installation of an LED. And Kedis82ZE8 also checked the resistance of the cargo LED and it isn't shorted out with 300Ω which means the LED itself didn't damage the RBCM. I simply think it was a bad design to leave cargo light unfused, and it got changed after 2016 MY.
 
Hi! Had the same problem. Was damaged transistor in the block RBCM.
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Would you mind to give us more detail about your experience on this? Did you use an LED as cargo light? Did your RBCM get damaged during installation of LED or like Kedis82ZE8 a couple of years after the use the LED?

BTW, if the component you circled is the culprit of your damaged RBCM, it's an IC, not a transistor just to the right. Hope someone like you can do component level fix as you had identified the bad IC on this damaged module. :)
 
Yeah... really interested if my VLED somehow caused this or just a flawed RBCM. Since there are some unknowns here I'll probably just leave the incandescent back there after repair.
 
I damaged my RBCM in the process of installation of additional LEDs. I didn't unplug the battery...(burn) and the mosfet Q15 was burned. There are two variants of such MOSFETs: SOT23-6 (replacement ZXMN6A08E6) and SC-62(replacement 2sk3065).
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Have you tried a different bulb? Is there voltage at all at the contacts?

Yeah stock and tested good incandescent bulb doesn't work either. I didn't test voltages further at that time as wife needed to use car. If vehicle wasn't under warranty I would dig into it deeper. I'll update thread on repairs. If this wasn't under warranty I would probably just tap into the 12V plug in the rear and use as a manual light. No other function of the RBCM was affected.
 
I damaged my RBCM in the process of installation of additional LEDs. I didn't unplug the battery...(burn) and the mosfet Q15 was burned. There are two variants of such MOSFETs: SOT23-6 (replacement ZXMN6A08E6) and SC-62(replacement 2sk3065).
Thanks for detailed info on what you'd found when you damaged the RBCM. If you could pinpoint the burned component, you can fix your damaged RBCM at component level by yourself with easy. I guess from my old knowledge a MOSFET power transistor loooks like this:
877px-D2PAK.JPG


And this has dual MOSFET power transistors packaged together as one chip like you mentioned - type SOT23-6 which is on our RBCM board:
FDG6322C%20FET%20SOT23-5.JPG
 
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