Said It Here

Key fob stops working after the car sits parked

When a vehicle sits parked for a period, battery drain from parasitic power draws can drop the 12V battery voltage just enough to put the keyless entry receiver into a low-power sleep mode or cause control module communication issues. Driving the car charges the battery back up and wakes the module, which restores normal remote fob functionality. Extreme ambient heat can also accelerate battery degradation or cause micro-outages in onboard computers like the infotainment system, contributing to intermittent electrical failures.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    Using the manual key lock/unlock
  2. 2
    Using the interior lock/unlock, window controls, and trunk latch buttons inside the car
  3. 3
    Replacing fob batteries
  4. 4
    Checking car battery health
  5. 5
    Manually unlocking the car with the physical key and waiting until after driving for the remote fob to function again.

In their words

Unedited, most upvoted first, each linked to the thread it came from.

I had to change out the battery in the fob this morning bc it said it was dead, tried starting the car and it wouldn’t start, and advice on what this could possibly be would be great.source ↗

AdHot6121 · r/AskMechanics · 2 upvotes

My key fob has got to where it will not work after my car has sat for a while, like in the morning or when leaving work.source ↗

Hot_Bar2766 · r/MechanicAdvice · 2 upvotes

Lately I’ve had to manually unlock my car using the key, unlocking remotely does nothing. But then if I drive somewhere, my key fob starts working again and I can lock and unlock remotely.source ↗

throwaway827367392 · r/MechanicAdvice · 1 upvotes

I did notice my infotainment randomly system reset a couple times lately. My car sits on the street and it gets really hot where I live 100+ degrees. Would that affect anything?source ↗

throwaway827367392 · r/MechanicAdvice · 1 upvotes

Where this came up

People with this problem also raised