weird electrical issue? BCM?

R

raining-turtles

Member
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CX5 Touring AWD
I went to go run to taco bell tonight and when I first went to start the car it failed to start, the green key light did light, but the gauge needles went all the way up then back to 0 and then all the (working) acc functions turned on. It did this about 3 times then started, however when it did a bunch of things were not functioning. The head unit went into the dim night mode, the blower fans for AC didnt work, the turn signals didnt work, no fog lights and no brights.
So I came home pulled the positive to the battery for 5 min, pulled all the connectors to the BCM and re-connected and then it all fired up just like normal. I am thinking that it is a possible BCM going out on me (and if so, I want to replace it ASAP before it fully cooks), has any one else had this happen? I have a 2013 touring CX5.
 
raining-turtles said:
I went to go run to taco bell tonight and when I first went to start the car it failed to start, the green key light did light, but the gauge needles went all the way up then back to 0 and then all the (working) acc functions turned on. It did this about 3 times then started, however when it did a bunch of things were not functioning. The head unit went into the dim night mode, the blower fans for AC didnt work, the turn signals didnt work, no fog lights and no brights.
So I came home pulled the positive to the battery for 5 min, pulled all the connectors to the BCM and re-connected and then it all fired up just like normal. I am thinking that it is a possible BCM going out on me (and if so, I want to replace it ASAP before it fully cooks), has any one else had this happen? I have a 2013 touring CX5.
Click to expand...

How old is the 12 V battery>?
 
raining-turtles said:
jsut replaced the battery 1.5 year ago... doesnt mean its not dead though.
Click to expand...

I would start with a simple test of the voltage at the battery terminals both with the car off and running.

Other issues can occur at the

1. start button (Be sure to press button fully and long enough)
2. brake pedal switch (wear item and issue on early 2013-2014 models)
3. shifter Park switch. (wear item and also issue on 2013-2014 models)

I would consider all of these items before the BCM.
 
mazdadude said:
I would start with a simple test of the voltage at the battery terminals both with the car off and running.

Other issues can occur at the

1. start button (Be sure to press button fully and long enough)
2. brake pedal switch (wear item and issue on early 2013-2014 models)
3. shifter Park switch. (wear item and also issue on 2013-2014 models)

I would consider all of these items before the BCM.
Click to expand...

OK, so this morning the car failed to start until I pulled the battery cable for about 5 min.
It would act normal (all lights and acc functioning, green key light on dash, solid green start button), however the starter solenoid would engage repeatedly (made a fast continuous clicking till I let my finger off the start button) with out actually turning the engine over.
After this mornings incident I am for sure going to do a voltage test. However, if it was either 1,2 or 3 that you listed the starter button should not have shown solid green and engaged the starter solenoid, correct? I did some research and it looks like most all of the symptoms yesterday were all controlled by the front BCM under the hood. However is it possible that this is a "low battery limp mode" of sorts?
 
raining-turtles said:
OK, so this morning the car failed to start until I pulled the battery cable for about 5 min.
It would act normal (all lights and acc functioning, green key light on dash, solid green start button), however the starter solenoid would engage repeatedly (made a fast continuous clicking till I let my finger off the start button) with out actually turning the engine over.
After this mornings incident I am for sure going to do a voltage test. However, if it was either 1,2 or 3 that you listed the starter button should not have shown solid green and engaged the starter solenoid, correct? I did some research and it looks like most all of the symptoms yesterday were all controlled by the front BCM under the hood. However is it possible that this is a "low battery limp mode" of sorts?
Click to expand...
Yes I agree 100% with your assessment.
Really sounds like a low battery voltage at the moment... either battery or alt.
 
I would have the battery charged and load-tested to see if it is good. If it is, at least you can rule that out as a possible culprit.
 
Just got home from work, did a few tests before i got pulled into cleaning a dog poop filled roomba... After sitting in traffic for an hour with AC running full blast, the running voltage was 13.6V and off was 12.3V. My terminals are fairly corroded so my plan is;
A: get jumper cables because for some reason I dont have any
B: clean off the connections and make sure they are nice and tight
C: go to the parts store and have them run tests on the ALT and Battery

the intermittentness of it makes me think it could be just a corroded connection, but it is still weird that the 2 occurrences have not been the same symptoms.
 
ok so went to autozone and had the clerk test the battery. from what he told me the battery is just fine. cleaned all the corrosion off all the terminals and wirebrushed the terminals and connectors. Now hopefully Im not stuck trying to get to work on time tomorrow.
 
Corrosion will be caused by bad battery cables.

My other car was acting goofy even with a new battery, and good charging. It would sometimes crank...other times not. Battery looked like it was being overcharged...a tiny bit of leaking out of the top.

My negative battery terminal was always corroded. I cleaned it a bunch but it stopped helping after a bit. I cut the terminal off the cable and internally, the wiring was ROTTEN...couldn't be seen from the outside. Luckily, the cable had enough slack, I could just strip enough off to get to good copper and use a torch and soldered on a new terminal.

No issues for 2 years now. Battery looks fine. ZERO corrosion. Lights and cabin fan do not surge when revving engine.

I'll wager you have the exactly the same problem starting. You have a bad connection at whatever terminal is corroding.
 
Last edited:
While it sounds like youre going the right direction, another cheap thing to check that caused a similar issue for me is the brake pedal switch. I replaced mine and good as new.
 
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