If you have already bought the Lexus UX model with a hybrid engine, you may be a little frustrated with the number of reports about that 12-volt battery performance. You may be surprised to know that the UX hybrid model still has a 12-volt battery. But yes, the auxiliary battery serves to start the gasoline engine and to run your accessories when the engine is not on.
In short, the 12-volt battery in your Lexus UX may go bad because of the power drain, long sitting, auxiliary equipment, software bugs, and some other issues that I want to discuss in this article.
Unfortunately, a lot of UX owners had to replace the battery or just found themselves stranded on the side of the road because the auxiliary battery was dead.
Where is the 12-volt battery in the Lexus UX?
The hybrid model of the UX has a special compartment for the Auxiliary battery in the trunk. When you open the trunk, lift the carpet and look to the right. There you have the compartment that you need to open to reach the battery. Please keep in mind that this is the auxiliary battery, not the hybrid battery.
Now, at least, you can find this faulty battery and replace it or recharge it with a charger or a booster. But let’s see why exactly this battery can go bad.
The common reasons for the 12-volt battery failure in the UX
The UX 250h is one of the most popular subcompact SUVs in the luxury class. The vehicle is really cool to drive, it’s very economical, and it offers a truly luxurious interior. And that’s why a lot of people choose this car when it comes to small hybrid SUVs.
I should fairly say that the UX hybrid is a very reliable vehicle. Its hybrid powertrain is based on the 2-liter Toyota engine and a very durable electric engine. The hybrid battery pack is just 1.4 kWh, so it won’t cost you a fortune when you need to replace it with a new battery pack.
And the only frustrating thing in this vehicle is its auxiliary battery which fails in almost all cars that have gone more than 15,000 miles. So, let’s see what can lead to this problem and how you can avoid it:
1. Software problem
Lexus is not known for a lot of software problems, but the UX became one of the first models with a lot of service bulletins that cover exactly the software issues. The UX has a problem with the Phone Home software. In its initial version, this software is draining the battery somehow. It just stays active all the time, even if you turn off the engine.
So, if your Lexus is sitting for more than two weeks, and it doesn’t have the latest update for the Phone Home function, it’s most likely that its auxiliary battery will lose all its juice. When you want to start the engine, it will seem dead.
2. Additional equipment
Although the Lexus UX has everything you need in terms of technology, a lot of owners will still want to include extra functions and will add some extra equipment. This may be a special phone charger, road camera, entertainment equipment, etc. Such equipment is usually plugged in one of the USB ports and it may stay on even if you turn off the engine. Your car may just sit one night and then refuse to start.
I would recommend turning off all the additional equipment that you have installed in your Lexus UX. First of all, the standard equipment should be enough for your comfort and entertainment. Secondly, the additional equipment will anyway kill the 12-volt battery xooner or later.
3. Just long sitting
While the hybrid battery that has 1.4 kWh of capacity will not die in two or three weeks without any action, the auxiliary battery may easily die in three weeks. You may be surprised to know that your Lexus does not charge the 12-volt battery using its hybrid battery. The only way the auxiliary battery can charge is from the alternator that is mounted on the gasoline engine.
So, sometimes it’s important to provide the auxiliary battery in the Lexus UX with the load test. Every Lexus dealership can make this test, but you can also go to any battery store, or just any repair shop that you trust and ask them to make the load test. If the battery fails this test, it should be replaced with the new one.
4. Old or worn-out battery
This is the usual reason why your car battery can fail. If it’s old or just weak, it’s not able to cope with all the work that it has to deal with daily.
Of course, you don’t tend to think that in your three-year-old Lexus, the auxiliary battery can be old. But this is the average lifespan of such a device. In a hybrid vehicle, the auxiliary battery has a lot of work to do. It actually supports almost all energy-dependent equipment in your interior, and it also starts the engine. The hybrid battery has only one task – to help the engine push your car and add some torque for better driving and optimal fuel economy.
So, about every three years, you will have to check the battery’s health and decide whether the auxiliary battery has to be changed.
What else will happen in the UX when the battery is low?
Once your Lexus battery goes flat, you may get some more problems like glitching assists, some error messages, and other issues.
One of the most common problems with the UX is the issue with the park assist. Even after you replace or charge the battery, your Lexus may still be telling you “Park Assist Is Unavailable”.
There is a simple fix for this problem. Park your car, then turn your steering wheel to the right till it reaches the limit, then turn your steering wheel to the left. Turn the engine off, wait for three minutes, and turn the engine on again. If this didn’t solve the park assist problem, you will most likely need a scanner to reset the code.
If there are some other error messages, warning lights, and error codes, you better go to the dealership or to the repair shop and have your Lexus diagnosed.
Can you jump-start the Lexus UX hybrid?
Actually, yes, you can jump-start this car just like any other vehicle with an internal combustion engine. But I don’t recommend this because when done incorrectly, this procedure can do a lot of harm.
So, for jump-starting, you better use a special booster. This is a small battery that can give a pretty strong current for a limited period of time. The booster is connected directly to the battery, and then you can start the engine using the power of the booster. After that, the auxiliary battery will start charging from the engine. And after some time, it should be okay to go further.
Jumpstarting your Lexus with another car is more dangerous. I will not provide you with the guideline on how to do this because you can easily find that online. Just be careful with every step you make and remember that repairing the electrical system of your Lexus will cost you a fortune.
Can Lexus UX start using the hybrid battery?
It’s quite obvious that when you are stranded on the roadside with your luxury SUV, you may want to know if you can start the engine using the hybrid battery. But, unfortunately, like almost any other full-hybrid or parallel-hybrid vehicle, your Lexus is not able to use the hybrid battery for cranking the engine.
Also, the UX hybrid doesn’t have any all-electric range, so you can’t drive without starting the gasoline engine. And this leaves you only one way to drive the vehicle – to start the gasoline engine using one of the ways discussed above.
How can I prevent problems with the auxiliary battery in my Lexus UX?
Unfortunately, it’s impossible to completely prevent these problems because the system may have some problems with the software and some other ways to drain the battery. But you can minimize your chances to get into this unpleasant situation.
There are two ways you can prevent your auxiliary battery from failing in the Lexus:
- Test the battery regularly. Your UX will get its regular maintenance at least once a year. When you take your SUV to the repair shop or to the dealership, just ask the mechanic to test the 12-volt battery. This will help you catch the moment when the battery is almost dead and just replace it or maybe maintain it by charging it to the full.
- Replace the battery at least every four years. Usually, after four years of driving, the auxiliary battery in any full-hybrid vehicle will be almost dead. You can keep driving your UX until it eventually fails. But you never know when and where this may happen. So, you may schedule the auxiliary battery change every three or four years and just avoid these problems.
Also, you shouldn’t let your SUV sit for too long. If it has already spent about a week in your garage, just take it for a ride. A low or dead battery is not the only problem that can happen with your Lexus hybrid vehicle when it sits for a long time.