CT5-V 2025 CT5V BW battery dead, drivers manual key entry not functional

[ngoni]

I read it differently. If the key is close enough to talk to the car, then even if the key is stationary, and sleeping, it still might be talking to the car but at a lower message rate. In fact the car has to exchange info with the fob to know the key is indeed in sleep mode. If I was still working and had access to an Agilent spectrum analyzer I’d do a test for that, record messages between the fob and the car to see what they are actually doing.

Here's an excerpt from an Ars Technica story on car theft techniques:

“Now that people know how a relay attack works… car owners keep their keys in a metal box (blocking the radio message from the car) and some car makers now supply keys that go to sleep if motionless for a few minutes (and so won’t receive the radio message from the car),” Tindell wrote in a recent post. “Faced with this defeat but being unwilling to give up a lucrative activity, thieves moved to a new way around the security: bypassing the entire smart key system. They do this with a new attack: CAN Injection.”

The rest of the article is on the "CAN Injection" method, but cars from the last few years have implemented countermeasures that make it less likely to succeed. Regardless it would be cool to capture the communication and be certain what 'sleep' means for the fob and car.

 

[+ManifoldPSI]

If you leave the hood and trunk popped open while in the garage for periods of time, the car won’t go to sleep and the sensors for them will be triggered and draw the battery down even faster.

Same instruction in 2024 5BW manual. Ill have to try it.

I leave my hood popped when car in storage. Could leave the trunk popped. Gonna check on it tomorrow but the battery will def be low. Gonna charge it full but when stored for more than a week I'll pull the neg cable at battery per the manual. (I'm used to pulling the red cable first but the 5BW manual says pull the neg.)

"Infrequent Usage: Remove the black, negative (−) cable from the battery to keep the battery from running down."

For years, I have been leaving the trunk popped on rear-battery-equipped cars parked in my garage when I connect a battery tender. What I do so I can lock the car but still keep the trunk open (so as not to squish/damage the tender cable) is use my fingers to push the locking mechanism on the trunk lock itself into the lock position, then shut the trunk carefully, knowing it won't be able to latch but will still look closed to most anyone who sees the car.

The car will then think the trunk is closed, enabling me to lock it, fit my car cover, trickle charge it and give no one a reason to look further. This works on my E46 BMW wagon, Evo, 5VBW and others.

You just have to remember not to slam the trunk lid or otherwise try to shut it. When you unlock the car, you can unlock the trunk as normal or use the manual rear trunk release if needed for some reason.

 

[Argent86]

Just back from storage - 5BW was in storage 10 days, fired right up but initially took a minute or so to "wake-up" the instrument cluster when I entered the car. Seemed to be in some kinda sleep mode or, was sleeping...had to wiggle some buttons to wake it up - or the dash is just slow after parking awhile. But, the hood pop didn't "seem to" accelerate draw down? If it drew down it was miniscule. I did double-click the key fob to lock the car which might put the car to sleep quicker? (not sure, thought I read so in the manual)

The other thing re battery draw down is that I never accepted OnStar or Sirius, so those radios might be more off than on.

After 10 days I had something approximately around 50% battery (guess). When I drove home 5 miles and put on the charger it was at 70%. I was expecting way lower than the 50% guesstimate but it held up this time.

ps. the tires temps were at 27F and I got low pressure warning from 1 tire. After 5 miles at 40mph the tires never heated up, in fact they dropped 1 degree per the dash readout. Got loose for a second in Sport mode, the summer tires are def not for these temps.

 

[Argent86]

For years, I have been leaving the trunk popped on rear-battery-equipped cars parked in my garage when I connect a battery tender. What I do so I can lock the car but still keep the trunk open (so as not to squish/damage the tender cable) is use my fingers to push the locking mechanism on the trunk lock itself into the lock position, then shut the trunk carefully, knowing it won't be able to latch but will still look closed to most anyone who sees the car.

Good one!

 

[DCV]

Sport mode on summer tires in winter? Yikes

 

[Todd]

Sport mode on summer tires in winter? Yikes

lol, makes for an invigorating driving experience.

And unless you specifically change PTM settings, the nannies will catch you if you go too hoonigan, anyway.

 

[Argent86]

lol, makes for an invigorating driving experience.

And unless you specifically change PTM settings, the nannies will catch you if you go too hoonigan, anyway.

I like what I hear with the pipes open and the back seat down. Shifting gears around town up to a whopping 40mph

 

[pkincy]

I presume you have been able to get into the car now. The next challenge you are likely to face is that your battery 'smart' trickle charger/tender may not activate to charge your battery. Many of the smart chargers are programmed not to trickle charge a severely discharged battery. By that I mean with less than 6 v of charge left. Why? I have no idea but it is frustrating when you have a trickle charger or two and have a very dead battery. I have a dashcam with parking mode that is very good at completely draining my battery. The fix is to have a second trickle charger and one needs a constant 12v mode. So you hook both trickle chargers up in parallel....blacks on black and reds on red. It is perfectly fine to use the under hood connectors. Set one trickle charger to the constant 12 v setting and the other to trickle charge for the battery type you have. AGM for most of us. The constant 12 v signal fools the other charger into thinking it is Ok to charge the battery and it does so. YouTube is a good spot for helping with this second charger method.

 

[rubberduck]

If you really want to know why a trickle charger won’t work when an AGM battery is deep cycled, the short answer is the battery requires sufficient current to bring it back. If you’re interested in more technical details, I can provide links. But you can also ChatGPT it.

I use 30A for my Jeep’s Odyssey AGM battery since that is what it requires minimum. - I deep cycle it and it’s over 8 years old. I have 15A available for my 5BW, but I don’t let the voltage drop very far either.

Other than buying an expensive battery charger, the best bet is to take it to an auto parts store and have them charge it overnight. Providing too low a current to the battery could potentially reduce its lifespan. Use the right tools for the job.