Push button start system trouble

V

vroom

Member
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CX-5 GS AWD 2014, Sky Blue Mika
After almost 3 years of trouble free driving I finally encountered my first problem this weekend. Both times it happened after I had stopped the car for about 10-15 minutes to pick up stuff at the store. The car would just not start anymore. The engine would not even turn. The push button would just toggle between off and accessories. After 10 to 20 tries it finally started both times. Good thing because it was minus 25C outside. What I know is:

-it's not a bad battery in the fob, I know about the fob next to the button trick, it does not work.

-yes I'm in park.

-yes I'm depressing the brake pedal.

When I get in the car, the key indicator in the dash lights green so the key is detected fine. As soon as I depress the brake the key dash light turns red and the light on the button blinks amber. According to the manual this indicates a problem with the push button ignition system.

The problem is intermittent which is bad for diagnosis but the second time this happened the check engine light came on which is good because it should help the techs find what's wrong.

I'm bringing the car in tomorrow (they had no openings today) and I still have to start the car three times until then, so hopefully I don't get stuck at work tonight. I've read in the manual that when this happens you can force the car to start with a long push of the start button, but it does not say how long. We'll see. Wish me luck!

Any ideas what I could suggest to the tech tomorrow?
 
Unfortunately so many possibilities in FSM. Relays, start/stop unit to interlock switches...

The dealer will likely be connecting their M-MDS unit to vehicle for troubleshooting.
 
From what I gathered so far there is a fairly good chance this is just frost or moisture in a relay. It seems consistent with the sequence of events: car starts fine and runs just enough to warm the car a bit, frost in a relay melts and causes a short, car doesn't start anymore. Let the car stand for a few hours: no problems, drive 10-15 minutes, etc. you get the picture.
 
Not sure about the brake switch, but I certainly am no expert... The reason I have doubts is that when I depress the brake, the key in my dash turns from green to red, so the car certainly detects the brake depression. Does that make any sense?
 
vroom said:
Not sure about the brake switch, but I certainly am no expert... The reason I have doubts is that when I depress the brake, the key in my dash turns from green to red, so the car certainly detects the brake depression. Does that make any sense?
Click to expand...

Makes perfect sense.

For safety and redundancy, the brake switch is actually two switches in one. One switch is normally open, the other normally closed. If the ECU detects both open or both closed it knows there's a fault but it doesn't know whether the brake is depressed or relaxed.
 
MikeM. said:
Makes perfect sense.

For safety and redundancy, the brake switch is actually two switches in one. One switch is normally open, the other normally closed. If the ECU detects both open or both closed it knows there's a fault but it doesn't know whether the brake is depressed or relaxed.
Click to expand...

You could simulate the brake being pressed by unplugging the switch and shorting the two outer pins together in the plug that normally attaches to the switch.
 
MikeM. said:
Makes perfect sense.

For safety and redundancy, the brake switch is actually two switches in one. One switch is normally open, the other normally closed. If the ECU detects both open or both closed it knows there's a fault but it doesn't know whether the brake is depressed or relaxed.
Click to expand...

Thanks MikeM, I understand now and it does make sense.

MikeM. said:
You could simulate the brake being pressed by unplugging the switch and shorting the two outer pins together in the plug that normally attaches to the switch.
Click to expand...

Probably not going to try that in the dark parking lot at -20C at my work place tonight, but thanks for the suggestion. From what I understand, a long press (I don't know how long though) of the start button forces the car to start even if it can't determine that all the safety requirements are met (car in park, brake depressed). I feel better knowing that I have that option in case it doesn't start tonight.
 
vroom said:
Thanks MikeM, I understand now and it does make sense.



Probably not going to try that in the dark parking lot at -20C at my work place tonight, but thanks for the suggestion. From what I understand, a long press (I don't know how long though) of the start button forces the car to start even if it can't determine that all the safety requirements are met (car in park, brake depressed). I feel better knowing that I have that option in case it doesn't start tonight.
Click to expand...

Mazda service info says the long press option only works a limited number of times (without specifying how many it is).

What I would try is a number of rapid taps on the brake pedal, you should only need to depress it 3/4" each time or so. Make small but sharp impacts with the ball of your foot so the pedal returns quickly. I think that is your best option without having to get on your back and fiddle with the switch itself.
 
MikeM. said:
Mazda service info says the long press option only works a limited number of times (without specifying how many it is).

What I would try is a number of rapid taps on the brake pedal, you should only need to depress it 3/4" each time or so. Make small but sharp impacts with the ball of your foot so the pedal returns quickly. I think that is your best option without having to get on your back and fiddle with the switch itself.
Click to expand...

Since both times it eventually started after 10-20 tries, your foot tapping technique makes sense (that is basically what I was doing, but trying the start button after each brake depression). Will do that tonight or tomorrow if I have problems before I go with the long press as a last resort. I'm sure they can reset the long press "counter" to zero again at the dealer if ever I need to use it, so I won't hesitate if tapping the brake repeatedly doesn't work.

Funny thing about this is that my 3 year warranty ends in about a month. For once, Murphy's on my side!
 
This is the main brain of the system.

Screen%20Shot%202016-02-15%20at%2011.46.57%20AM.png

Screen%20Shot%202016-02-15%20at%2011.47.08%20AM.png
 
This start/stop unit is attached to the steering column. Here are instructions in FSM on how to remove unit...

Screen%20Shot%202016-02-15%20at%2011.51.27%20AM.png
 
I have my car in at the dealer today, and they just called me with the verdict. According to the code, it was a relay that had intermittent failures. Apparently there is a TSB for this affecting mostly 13s and early 14s (like mine), although I could not find it in the sticky thread. The TSB calls for changing 5 relays because water/condensation can get into them in cold weather, which they did (even though only one was failing for me). The girl told me I was lucky it had not happened before, as last year they were getting calls for that almost every day. Some people even had to have their car towed because they could not get it to start.

They told me the brake pedal switch causes a different code to be logged, so they ruled that out.

I'm driving an almost brand new 3 today (less than 600 miles). It's ok but I was expecting a bit more "oomf" in response to the gas pedal, considering the lower weight of the car. Can't wait to get my CX-5 back!
 
They told me they were in the fuse box, which makes sense as several relays are often located there.
 
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