2014 CX-5: All Warning Lights Going Crazy, Help!

So, I have a 2014 CX 5 with 69,000 miles. As others have said, my car has started randomly flashing brake system, traction control, low tire pressure and check engine lights. I took it to my mechanic and he changed out brake switch, didn’t solve the problem. Went through all the codes and started looking for shorts in electrical. Found several corroded connections, cleaned them up, still no change. He said he thought it was the control module, recommended taking it to dealership. Dealership said brake switch had been installed incorrectly, replaced switch and sent me on my way. Lights came back next day, and as described car wouldn’t start and brake felt rock hard. Back to the dealer, they have had the car 25 days, they are taking bumpers and body panels looking for electrical harnesses. I’m at my wit’s in. IDEAS?
Thanks.
 

CarpeDiem

Under Pressure
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Superstitions
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2021 Carbon T
As above, the most common cause of what the OP describes is a failing battery. Since the dealer has had the vehicle for a month I assume they charged the battery - but just charging is not enough. The battery should be electronically load tested, not just voltage checked. The dealer should have installed a good battery to see if that eliminated the problems. How old is the battery?

Of course it could be another issue since the vehicle may have been a victim of a flood, but a failing battery should be the first thing checked. This applies to most modern vehicles, the huge number of sensors and processors can be very voltage sensitive, and even a small voltage drop under load can cause all kinds of warnings and problems. Just because there is enough voltage to start the engine doesn’t mean the battery is any good.

The hard brake pedal is because the vacuum has been depleted - without the engine running there is no more vacuum.
 
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yrwei52

2016 Mazda CX-5 GT AWD w/Tech Pkg
Contributor
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Plano, Texas, USA
So, I have a 2014 CX 5 with 69,000 miles. As others have said, my car has started randomly flashing brake system, traction control, low tire pressure and check engine lights. I took it to my mechanic and he changed out brake switch, didn’t solve the problem. Went through all the codes and started looking for shorts in electrical. Found several corroded connections, cleaned them up, still no change. He said he thought it was the control module, recommended taking it to dealership. Dealership said brake switch had been installed incorrectly, replaced switch and sent me on my way. Lights came back next day, and as described car wouldn’t start and brake felt rock hard. Back to the dealer, they have had the car 25 days, they are taking bumpers and body panels looking for electrical harnesses. I’m at my wit’s in. IDEAS?
Thanks.
Honestly for this kind of problem dealer still is the best place (or the only place) to find the culprit. A Mazda dealer has factory trained master mechanics、factory technical info and support、and Mazda computer equipments to help them diagnosing all kind of issues. Since your CX-5 has been in Mazda dealer for about a month, battery part should have been checked long ago, and they’re now taking down bumpers and body panels looking for problems on electrical harnesses. I’ve seen reports here on similar problem and a bad grounding usually was the culprit. A couple of times It took Mazda sending field engineers to the dealer and eventually resolved the problem. But those were warranty repair and Mazda had to go all out and fix the problem. If your 2014 CX-5 with 69,000 miles has no warranty, I wonder if it’s worth it to spend huge repair bill to fix the car. A car which is going to take more than a month to fix (if fixed) by a dealer, it has to come with an expensive bill.

Many years ago my previous 1987 VW Vanagon GL Syncro developed unstable idle and my VW dealer had no clue to fix it after several tries. Eventually VWoA sent a field manager to diagnose the problem. After he replaced the idle stabilizer and the problem was still persistent, he decided to replace the whole wiring harness in (rear) engine compartment. He did fix the problem with that, and luckily the Vanagon was under warranty at the time.
 
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Mazda, CX5 GT, 2014, wife has a 2014 Mazda3 GT
When I had the issue of all the lights coming on, it was the battery. The first time it needed a new battery, since the original was 5 year's old. The second time, which was only a few months ago, was because the replacement battery was defective.
 
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