Hey everyone,
I’ve been dealing with a really strange issue on my 2010 RX450h and I’m hoping someone here has seen this before.

Whenever the temperature drops below about 45°F, the car refuses to unlock with the key fob. The smart key doesn’t get detected unless I touch the Start button with the fob. After it starts, I get these warnings on the dash:

• Check AFS System
  
• AFS OFF
  
• Traction Control
  

I also notice the anti-theft/security light doesn’t blink like it normally does.

Here’s what I’ve tried so far:

• New key fob battery
  
• Tried a second (new) key fob
  
• Had the 12V battery tested at multiple places and was told it’s “good”
  
• Car starts and drives fine
  
• As soon as the weather warms up the next day, everything works normally again
  

The problem only happens when it’s cold, and we don’t get freezing temps often where I live, so it’s been really hard to reproduce.

Has anyone experienced something like this? Could this still be a 12V battery or grounding issue even though the battery tests fine? Any ideas or places to check would be appreciated.

Thanks!

 

How old is the 12 volt battery? What was the voltage when tested? Both off and with car running, although with a hybrid this is difficult.
12 volt batteries do last for many years in a hybrid and may pass some tests but still need to be replaced.
Did anyone check for stored codes?

I suspect you just need to buy a new 12 volt battery.

 

Many things come to mind.

1. 12V battery maybe be weak below required minimum below 45
2. Has anyone checked the trunk area where the battery sits. Some folks have reported standing water.
3. Remove all remote fobs form vicinity of the vehicle to rule out interference.
4. On a really cold morning use the key to enter the vehicle and see if the inside push button lets you lock/unlock [this bypasses the remote receiver and issues with signal being received from the key fob]
5 Try with the second key fob.

Any history of repair/tampering with electrical?
Any aftermarket accessory?

There are a few unexpected lights glowing in the dash? Can you please list all codes. [one thing I might try would be clear all codes, there are some downside to this so walk on this path with care]

Salim