2018 Mazda CX-5 Various Electrical Issues

[CycloneCX5]

TLDR: Lift gate, infotainment screen, head up display, key less entry, keys, heated seats, heated steering wheel, interior lights, USB’s, and trip monitor stopped working suddenly. Car runs fine. Battery checked multiple times and showed to be “good”, and no fuses appear to be blown.

I have a 2018 Mazda CX-5 Grand Touring AWD. About two weeks ago the lift gate started to intermediately not want to open and give 3 beeps. It would not open with the key, rear button, or driver side button. Disconnecting and reconnecting the battery would temporarily fix the issue or over time it would decide to work on its own, but it kept returning.

A week after this started, I got a check engine light and took the car to O'Reilly to get the codes checked and to get the battery checked. The codes were U0100, U0115, U0121, and the battery and alternator showed good on the tests with the battery installed in the car. The check engine light would go away and come back randomly it seemed.

Several days later it all got worse. The lift gate issues persist but now the infotainment screen (tried back+nav+mute but nothing happened), head up display, key less entry, keys (not responding to both keys and have to place them next to start button to start the car), heated seats, heated steering wheel, interior lights, and USB’s in the console don’t work. Also the trip monitor resets after each drive. I took the battery out of the car and got it tested again at O’Reilly and the battery tested good again, it is an Optimum RedTop that is 2.75 years old. I tried checking all the fuses in the engine compartment and under the steering wheel and didn’t see any that looked bad.

The car seems to run fine otherwise. I just have to unlock/lock the car with the physical key.

Does anyone have any idea what could be causing all of these issues?

 

[Moonlighter]

If possible I would try a different battery. This still sounds like a dodgy battery or a bad connection to me.

i assume that you checked the battery cables for corrosion and cleaned and TIGHTENED the lugs when you put the battery back in?? They need to be bright and shiny and TIGHT.

How old is the fob battery? If any doubt its cheap to put a new one in there.

 

[Ranman57]

Just a long shot here but any chance you have critters under the hood chewing wires? Happened twice to a step-daughter's Ford SUV, car ran both times but all sorts of bizarre electrical gremlins appeared.

 

[Mazdiod2]

It might be something unusual, critters are a possiblity, as this is the time of year they plan invasions.
Maybe a bad ground somewhere important, as all of the codes refer to various communication modules.
Do you drive through deep water on the way to work?

 

[N7turbo]

Just a long shot here but any chance you have critters under the hood chewing wires? Happened twice to a step-daughter's Ford SUV, car ran both times but all sorts of bizarre electrical gremlins appeared.

It might be something unusual, critters are a possiblity, as this is the time of year they plan invasions.

My Dad had a squirrel chew through his Lexus wiring harness, so yeah.

Also it's possible one of the CAN bus modules went bad. I would see if those functions all route through the same module. I know this isn't Mercedes, but they are a known failure point on those cars. Especially when water leaks in...