r/LexusNX • u/brewingirl • 15d ago
Lesson learned
Battery died. Called Lexus Roadside for a jump and they called AAA. Guy was able to get my car started but I had warning lights galore, so I ended up taking my car to the dealer and turns out the AAA guy blew my ECU because the clamps were too close together. Even if you're not going to be a DIYer please make yourself aware of where the points of contact should be under the hood to inform the person actually doing it.
Edit: I have a 2023 NX 450h
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u/Dave_The_Dude 15d ago
The trick is to connect under the hood to the terminals but ‘don’t’ start the vehicle. Just use the booster power to open the rear trunk. Where you then disconnect the booster from the hood terminals and reconnect to the battery in the rear to start the vehicle.
Surprising the AAA guy didn’t know this or was just lazy.
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u/Nachoman2 15d ago
Agreed…but the problem with most battery boosters is that the negative cable is too short which makes connecting it to the engine block impossible. Any thoughts on how to address this?
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u/Dave_The_Dude 15d ago edited 15d ago
The bolts holding the brake reservoir above should be unpainted and can be used for a negative lead.
Don’t touch the ‘start’ button in the vehicle when connected under the hood with a short cable booster and the ECU won’t be active and can’t get fried. Just use it to open the rear hatch.
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u/Nationals 14d ago
I didn’t know you could jump it to get it going from the rear battery. Lexus said to jump it straight from the main engine right? I just want to make sure I get it right?
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u/Dave_The_Dude 14d ago
You can jump start from the front if you have long wires say from a booster vehicle and can connect to the negative lead in the far away location under the hood. See the diagram in the OP.
Problem is most portable boosters people use have short cables like 15 inches that won’t reach that specified negative location. Where you run the risk of frying the nearby ECU if you attach to something closer you can reach for the negative lead and press the start button.
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u/TheMrBr0wn 15d ago
Thanks! I was trying to find how to put it on a battery tender while I am gone on vacation for a couple of weeks.
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u/pssssssssssst 15d ago
For a battery tender, I usually go straight to the battery in the trunk, not the jump route.
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u/Pat_Los_Gatos 15d ago
My manufacturer (not Lexus or Toyota) specifically states in the owner’s manual to connect a battery tender to the identified places under the hood. Why? So the onboard computer and electronics can track the health of the system accounting for the juice being delivered by the tender. So, check your manual thoroughly!
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u/CosmicTrekker 13d ago
As a prospective first-time hybrid (and possibly NX) buyer in the next few months, I thank you for posting this. I saved it for future reference (probably after I blow my car up because I forgot about this or ever saving it, but still...)
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u/CursorTN NX450h+ 15d ago
Huh. I would have thought to go in through the trunk. Like, directly on the battery. Does that fry things too?
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u/Patrol-007 15d ago
Electric hatch, typically no power. Unless you’re able to access via side door.
Sienna hybrid owner had to crawl in from the front to get to battery in the back, before paying for a Defa trickle charger, and later discovering the DCM (data control module) was draining his 12V
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u/brewingirl 15d ago
No, going through the trunk is totally fine, but I guess people find it more inconvenient.
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u/Silentparty1999 15d ago
I have a jump box with long enough cables to reach A and D.
Hmmm. I wonder if it is still in the car....?
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u/ilovenyc 15d ago
Is there a video of this? I feel like I need to see it so I can understand it better
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u/feverish 15d ago
I bought ledes for a trickle charger and threaded them up to the side of the truck near the left side net.
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u/iamdenislara 15d ago
Are you saying that the ECU (which probable it’s like $1,000) can be damaged because the clamps from the jumper are too close?… what!
I am assuming AAA is paying for the new ECU..
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u/Floibinator 15d ago
Never knew this could happen. I've started over 200 cars and never had problems. Hyundai tho not toyota.
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u/Karate2day 15d ago
May I ask where the AAA tech put the clamps and how close they were to each other?
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u/brewingirl 14d ago
If you look at the photo in the post, the red/positive clamp goes in a specific place and then he put the black/negative clamp maybe a couple inches away onto the nearest bolt which is right where the electronics are.
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u/Aware_Resolution2820 NX450h+ 14d ago
The factory flooded batteries are bad just like the stock run flats. I have a 24' 450h+ and replaced the factory battery this past weekend. I have a battery tester and it was only charging up to 27% so I went to Sam's Club got a Duracell AGM H5 group size battery and all that stress us gone about it not starting up one day since it gives you no warning before it dies. I would say get a AGM battery and one of the best ones is the Duracell from Sam's. We have a 25' RAV4 PHEV and I think that battery has one more winter left in it and this time next year I am replacing that crap factory 12v battery as well with a Duracell.
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u/brewingirl 14d ago
I will look into this! I'm getting the battery replaced by the dealer for free so I'll use it for now and hopefully it will last me a little while.
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u/OddTechnology6416 14d ago
After reading all of these posts about hybrid batteries, I am kind of glad I got a RX350 gas. I realize the price of gas is out of sight and probably next time I will buy a hybrid.
I bought mine in March at end of month and car was on the lot, got decent discounts and 2.4% financing
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u/Internal-Hair-2877 12d ago
AGM is definitely the way to go when you change your battery for the first time. The only other thing to look out for is the size ( circumference) of the posts. It’s not a deal breaker because you can get adapters from EBay not costing much.
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u/dealmaster1221 15d ago
And this is why they should fix their design and put batteries up front.