Water damage to body control module on Mazda CX-9

Problem Description and Possible Solution

Various electrical issues may develop related to the body control module (BCM). There have been reports of water damage to the BCM caused by clogged or damaged sunroof drains. It is recommend to periodically inspect the sun roof drain for debris and clean as necessary.

Problem Data
RepairPal Verified
Average mileage: 72,800 (23,000–167,800)
7 model years affected: 2007, 2008, 2009, 2010, more2011, 2012, 2014
31 people reported this problem
Viewing 1 - 20 of 20 comments
Alarm going off randomly, TCS lights, parking break light, oil light, BMS light, traction control, and interior lights with door ajar lights - all randomly going off and on while driving and/or holding still! Only happens on rainy days.

Mechanic did NOT find/fix this problem - he thought it was related to needing a new bearing (not). Fixed the bearing - still have all these problems. Now we are attacking the BCM ourselves.
Problem started when noticed my passenger side floor soaked, since I use the rubber floor mats I didn't notice this problem for some time. It was after a heavy rain that enough water came in and puddle of water was sitting on top of the mat. I had to use a wet vac. The dealership was useless in finding the problem. Since then after looking up the problem on the internet and seeing that it's an acurrance I've been cleaning out the ducts. Now I'm reading it can be a clogged a/c line is clogged. Enough said that now after have car in the shop getting ready for a long trip (just having fluids, etc being checked)the shop sees the parking lights on the next morning after a heavy rain. They discover more water in car and the module is wet, now I can't take care on the trip. they try to dry out the module. But after picking up the car the BSM, TCS, brake light and tc symble are all on. This car has nothing but problems since I got it new. And never once could the dealership find the problems that I had taken it in for. This car is well cared for and hardley driven to warrent these kinds of problems. I am at a lost at dishing out hundreds of dollars for repairs when the car is not abused.
Water comes in through the windsheild and drips into the dashboard. It was poorly sealed but Mazda blames it on a car repair that was no where near the problem Now I have electical problems that they won't cover.
It started with the alarm going off after I would lock the door (or let the car auto-lock). I couldn't get the alarm turned off, so I disconnected the battery. The alarm would then randomly and periodically do the same thing, but only after a rain. Then just as random, the TCS, tire gauge, and ABS lights would come on. The trick I learned to turn those lights off was, while in park, to pull the steering wheel all the way to the right, then all the way to the left. After driving for a moment, the lights would go off... for a time. Today, I came out to find a dead car and my hazard lights dimly lit. I hope its safe to say the BCM is the cause of this before I go and replace it.
Alarm goes off when it rains. Dash shows that a door is open but they were all closed. Now the rear wiper won't turn off.
Same issues as described by others: when it rains heavily I begin having multiple electrical issues-car alarm goes off for no reason, door remote will not work, all warning lights illuminated. Had wet headliner on one occasion and today found moisture under upper left driver side floorboard.
When it rained the tcs light came on, indicators won't work, interior lights won't work, keys won't work, handbrake light on, oil light came on. To fix this we took out the bcm on the left front passenger side apart and cleaned all connection and plugs with an electrical spray and put back together. Problem fixed there was a couple of plugs that had slightly corroded from condensation, when sprayed and cleaned works perfectly.
Abs brake light on , anti skid light , oil light on check engine light 3 alarms when it rains and they will not clear
My TCS light in the dash and the one on the on/off button flickered the other day out of the blue when it was not raining. I did recently park under a pine tree that shed a lot of needles on my car and I'm reading here thinking my sunroof drains could very well have clogged and the time it rained the day before the issue presented itself, the sensor could have been water damaged. My local Mazda Dealership is in Kirkland, WA, and I called them but they want to charge a lot just to look at it, (not even quoting me yet for the parts they'll need) and say it is not covered by warranty or recall. Very disappointing.
BCM Soaked from heave rain.
Won't lock know except when it sits in the hot sun for hours.
The CX-9 showed a number of electrical issues (turn signals, door locks, other components did not work). Took it to the dealer who replaced the BCM. There were no signs of water damage. Four weeks later, after a heavy rainstorm, the BCM failed again (hazard lights would not turn off). The dealer determined that clogged sunroof drains caused water to leak onto the BCM.
Water on drivers side floor during heavy rain storm. Electrical failures similar to above stories. After having the CX9 at the dealer a week they discovered a leak between the windshield and the body frame. Water was entering between window seal and frame, leaking on BCM and other critical electronic components. After all repairs were completed I was looking at $1800. Due to being on warranty still Mazda picked up the cost completely. I have 100K on the rig now and the problem never returned. I live in the NW and we get quite a bit of rain.
I was in the house one night (while it was raining) and my car was parked in the driveway. All of a sudden the horn started blowing continuously. I went out thinking my alarm had been triggered. My keyless remote would not unlock the car or stop the "Panic" horn blowing. I opened the door with my manual key and turned the engine on thinking that may stop it, but no success. I opened the hood to disconnect the battery and when I did, I could smell an electrical burning smell. The horn was blowing so LOUD it was hard to think. I disconnected the battery and the horn stopped, but the smell remained. I let the car sit and the next morning re-connected the battery. These are all the items that didn't work. The electric door locks, the keyless remote, my turn signals, rear powered hatch and I had the following warning lights on my dash....ABS, 4x4, Traction Control, and engine. I have read about numerous customers having this experience with their Mazda vehicles (not just the CX-9 owners). There is a problem with the sunroof drains getting backed up and the water then goes into the cabin and fry's the BCM unit. Mazda needs to address this and take care of their customers, not have their dealerships quote $1,000 + to replace a silly circuit board. This very well may be my last Mazda if this is how they treat their customers.
During heavy rain the light and horn randomly go off, I have cleaned the drivers side drain.
Water caused bad bcm and all warning lights came on no blinkers and locks not working!!!!!!!
Second BSM body control module. I was driving to the airport and it was very slushy and heavy snow. I got back from the flight and all my dash warning lights along with the alarm kept staying on. No power locks. Randomly I could get things to work for an hour. Dealership wants to replace module with no explanation. I will contact them today to talk about if it was water damage and how they expect the water damage is happening. Sounds like sunroof drain might be suspect.
I have recently replaced my control module....
Leaks have after hard rain, have trashed our BCM. First noticed standing water in passenger side. Thought it was AC condensation. Blew it out. Still got leaks sometimes in driver's side. Doors won't lock, turn signals won't work, alarm would randomly sound--but that has went away.
Media button, blue tooth button don't work after rains and rear a/c fan blows on high for about 5 minutes after car is turned off. Also, low beam headlights alternate blowing at a rate of about one per month. Most recently, the rear wiper comes on and won't turn off.
Same thing. Dealership replaced in cabin air filter as though that would solve problem. Water comes in through windshield and now have an electrical problem that they will not cover under warranty. They are citing a minor accident where fog light was replaced as cause for windshield problem that has nothing to do with it. It is their way of getting out of repair.