Rear Cross Traffic Alert - where is sensor located?

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Mazda CX5 Grand Touring
Recently had my rear tail lamp assembly in my 2017 CX5 replaced by a local mechanic (it was cracked and wouldn't pass inspection). I just noticed that the Rear Cross Traffic Alert has stopped working since it was replaced. Thinking he accidentally disconnected something or somehow blocked the sensor. Before I go back and ask him to fix that, I wanted to know for myself where the sensor is, and where the connection is (something I can easily fix?) I can't find anything in the manual other than how the RCTA works, and that it's connected to the rear BSM system. Anyone here know? Car is still under warranty but really don't want to go to the dealer since I didn't use them to replace the light (they wanted almost twice as much to replace)

TIA.
 
The sensor is behind the side surface of the rear bumper fascia.

The tail lights can be removed and installed without removing any other bits or pieces. And you'd only connect / disconnect the tail lamp harness (it's all that's behind the tail lamp).

If your tail lamps are working fine I'd suggest this is an unhappy coincidence. If the tail lamp also isn't working I'd be looking deeper.
 
The sensor is behind the side surface of the rear bumper fascia.

The tail lights can be removed and installed without removing any other bits or pieces. And you'd only connect / disconnect the tail lamp harness (it's all that's behind the tail lamp).

If your tail lamps are working fine I'd suggest this is an unhappy coincidence. If the tail lamp also isn't working I'd be looking deeper.

BSM System

I know the image in the link is not referring to the KF (2017+), but the location is the same.

The Rear Cross Traffic Alert uses the BSM Control Modules underneath the bumper as Studum already pointed out.
 
The sensor is behind the side surface of the rear bumper fascia.

The tail lights can be removed and installed without removing any other bits or pieces. And you'd only connect / disconnect the tail lamp harness (it's all that's behind the tail lamp).

If your tail lamps are working fine I'd suggest this is an unhappy coincidence. If the tail lamp also isn't working I'd be looking deeper.

Yes the tail lamp was easily removed from the outside, but to connect all the wires properly he had to pull out the panel inside the trunk. I watched him do it; he was thinking was as easy as you say but there was a wire going inside that had to be disconnected. That's where I'm guessing something went wrong.
 
To add to this, in case it helps: this was the lamp that's on the rear side, not on the hatch.
 
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He didn't have to replace that harness. If it's the same housing the bulbs and holders could've popped right into the new housing. Oh well, what's done is done.

The tail light harness connection in vehicle is indeed behind the plastic panels either side. If that's the only area he was it still shouldn't have done anything. The harness is dedicated for the lamps away from other things.

The rear BCM is left side a little further behind the panel. I would imagine the sensors work through there in some way. If he really goobered up and it's related I suppose there's a chance something got messed up. I'd call it unlikely though.

Side tail lamp comes off with a couple of screws, then just pops out. Still no bumper or under car work needed.


**Edit** per the diagram attached there is a BSM module that does connect to the RBCM. I don't know where the BSM module is. If it's back there in the same area and it was inadvertently damaged or disconnected it's possibly related. In the end you need to troubleshoot the BSM independently.

Before you go too far though, have you confirmed it's turned on and not turned off by mistake?
 
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Yes the tail lamp was easily removed from the outside, but to connect all the wires properly he had to pull out the panel inside the trunk. I watched him do it; he was thinking was as easy as you say but there was a wire going inside that had to be disconnected. That's where I'm guessing something went wrong.
The outer tail light assembly is easy to be replaced, and the plastic panel in trunk right behind the tail light unit needs to be removed to loose 3 bolts and the lens assembly hence can be removed. You cant remove the lens assembly from outside, or it would get stolen easily! Theres a connector also needs to be removed from lens assembly and plugs in to the new one.

Judging by your description, the local mechanic seemed to be doing nothing wrong, as the connectors for RCTA radar sensor is hidden way below, and you have to remove the rear bumper to see the connectors for it.

Is your BSM still working? As it uses the same sensors at rear corners from RCTA. And I agree with Studum, check the setup at infotainment system and see if BSM / RCTA got turned off.
 
The front BSM seemed to be working this morning, the light on the mirror went on when someone would pass me on the highway. When I went to change lanes with a car near my rear bumper, however, the light didn't display (and it typically does, usually it's ultra sensitive). I know it's the same sensor as the RCTA so figured it was all connected. All was working fine until I had the lamp assembly replaced. Maybe just a coincidence, but if it wasn't something mechanic did, I'm concerned that if I take it to the dealer under warranty they'll try to blame it on the mechanic.

I'll double check the settings when I get back in my car after work and report back. Thanks everyone.
 
The front BSM seemed to be working this morning, the light on the mirror went on when someone would pass me on the highway. When I went to change lanes with a car near my rear bumper, however, the light didn't display (and it typically does, usually it's ultra sensitive). I know it's the same sensor as the RCTA so figured it was all connected. All was working fine until I had the lamp assembly replaced. Maybe just a coincidence, but if it wasn't something mechanic did, I'm concerned that if I take it to the dealer under warranty they'll try to blame it on the mechanic.

I'll double check the settings when I get back in my car after work and report back. Thanks everyone.
Is your replacement rear light assembly OEM? You should take the CX-5 to your Mazda dealer for warranty service to fix the RCTA issue. You don't have to mention the replacement of outer rear light assembly as it's totally un-related to BSM / RCTA system or rear radar sensors.
 
Is your replacement rear light assembly OEM? You should take the CX-5 to your Mazda dealer for warranty service to fix the RCTA issue. You don't have to mention the replacement of outer rear light assembly as it's totally un-related to BSM / RCTA system or rear radar sensors.

Good question - just checked my invoice and it's A/M. Hmm.

The dealer noted my cracked tail light when they last changed my oil, so my concern is they already know it has been replaced and not by them. Dealer quote to fix it was $500-600 so I said nope and went to the mechanic. Still, doesn't hurt to ask dealer I guess .. I'll be due for another oil change soon.
 
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