Hi folks. I have a 2019 CX-9 which yesterday failed to start on me for the first time.

Summary of what happened:

- Car failed to start. Dashboard indicator lights kept flickering. Dashcam powering on/off quickly.
- Used multimeter to check car battery voltage, and it was low, about 7.4V.
- Used an emergency jump-starter and got the car started within minutes.
- Drove around for about an hour and no problems ...
- ... except that power liftgate not working at all. No beeps even.

What's weird is though moments before trying to start the car, I wanted to load some stuff in the trunk and used the button on car's rear to successfully open and close the power liftgate. But right afterwards, car won't start as mentioned above. Since then, power liftgate hasn't worked even though the car itself powered on.

My dilemma now:

Since the car is 4.5 years old, I assume car battery just needs replacement, which I'm fine doing myself. But I don't know how to fix the power liftgate issue. Some folks online have mentioned that disconnecting/reconnecting the car battery helped 'reset' the electronics, and got the power liftgate working again. However I then came across another set of online posts where people said that when they disconnected & reconnected their CX-9's car battery (or installed a new battery) without using a 'memory saver' ( ), their car's electronics showed malfunction warnings because the car didn't expect all its electronics to *completely* loose power. So I'm worried that if I try to disconnect/reconnect the battery to try to 'reset' the power liftgate, I might face other issues.

Any suggestions on what I should do ? I can take my CX-9 to a Mazda dealership to have them replace battery and fix the power liftgate issue, but they'll most likely charge me a whole lot more for something I could probably do myself.

Needs suggestions on what to do.

 

The first thing to do before assuming anything is to have your battery load tested. The next thing is to look at both the terminal leads on the battery then the positive cable going to the starter and lastly the ground for all have good clean connections
After that you then go to the OBDII diagnostic connector with a good quality Scanning tool and pull the ECU information for active DTCs, permanent DTC and status of the I/M monitors.

Once you do that you can post the results and some of us can suggest the next plan to finding your problem.


The Battery "MUST" be at least 12.50 volts for a proper load test of the battery.

PLease dont respond with you know the battery is ok because.... a) it is new or fairly new or b) because you drove around and it charge up to 12+ volts. Neither is any indicator of the battery's health status!

 

Welcome to the forum

 

Thanks for your reply.

So you mentioned 3 things in this order:

1. Have battery load tested.
2. Make sure both positive and negative cables are okay, and their connections to the battery are good.
3. Use an OBDII tool to look for diagnostic codes.

Besides Mazda dealers (since they'll simply rob me to check this stuff), do shops like AutoZone help with the above 3 tasks ? I'm no car expert so my analysis will likely be lacking.

Having said the above, I'm pretty sire the needs a replacement in any case because 1) it's at least 4.5 years old, if not more (prior to me getting the car from dealership), 2) over the last year, sometimes I've heard the crank of the being a little 'slow', 3) I also have DroneMobile for my car which monitors battery voltage, and often times I've seen is drop to low levels.

So I'm virtually sure I'll need to replace the battery. I'm just not sure whether I should be the done to do it, or a Mazda dealer, due to the other power liftgate issue, and what I mentioned about all computer data being 'reset' when the battery is disconnected. I fear it might cause more problems.

 

Changing the battery should not be an issue. You may lose some memory features like preset radio maybe small easily reset amenities. Nothing major. However, if you are really concerned have a service shop with an ASE sign change your battery for you.
I would not recommend the use of AutoZone for your Mazda to change the battery. While they do well in some area's their employee training program is far short of what it once was (if ever) and they could unknowingly cause unrelated problems. Just saying. As for ECU and getting the information... definite NOT. They can (my turtle could) get basic ECU trouble codes but ask the average employee for the other and you get the "dumb" expressions on their face. LOL

Based on your second response .... it long overdue. Btw monitoring battery voltage is really no way to determine the heath of a battery only your alternator/generator and that is not always the case because the charging system is ECU controlled.


ASE