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.