DIY: Add Magnetic Emergency “Door Unlock” Function
This simple design will enable you to unlock the driver’s side power door lock on Tundra with the “swipe” of a magnet.
If you have an interest and about $10 to invest please read on and I will try to explain How-To-Do-It.
From time to time I have needed to unlock my vehicle when I didn’t have the key or the remote control handy.
Maybe I was an “air head” and locked the key inside, or I lost the key and needed to get to my cell phone inside my vehicle. I guess there could be any number of reasons why I might want the ability to unlock the doors without having the key or remote handy.
I have installed this system in very vehicle I have ever owned with power door locks.
How It All Works
Tundra Door Unlock Function
The doors on your Tundra are unlocked when a “Momentary Ground” signal is sent to the Main Body ECU.
The Main Body ECU then sends power to the door unlock solenoid and presto, you can get in.
It is really that simple.
Magnetic Unlock Design
Please click on first thumbnail below to view a drawing, which I will describe here in words. (unlock1.jpg)
This design employs a small “reed switch” which you hide in the location of your choice.
This reed switch is nothing more then a small switch sealed inside a glass envelope. There are two small metal fingers (contacts) inside.
These fingers are “close” to each other but they do not touch. This is called the Normally Open position of the switch. These contacts are not mechanically or electrically connected. Think of this as the switch is “Turned OFF”
When a magnet is “swiped” near the reed switch, the two fingers (contacts) inside the glass envelop bend and touch each other. When they make ‘Contact” they are mechanically and electrically connected. Just like any other switch, this one is now “Turned ON”, for a moment.
One side of the reed switch is connected to (tapped into) the “Door Unlock Signal Wire” going to the Tundra’s Main Body ECU. The other side of the reed switch is connected to the Tundra body to supply the needed “Ground”.
The reed switch is hidden behind a plastic body panel/part on the outside of your Tundra. The reed switch is held in place (glued) with clear RTV behind the plastic panel. Think cowl molding by the wipers, or inner wheel well, behind the front grill, behind plastic of front bumper. Pick your plastic poison; there are plenty of plastic locations to mount the reed switch behind.
When you “Swipe” a magnet over the hidden reed switch location it causes the a “Momentary Ground” to be sent to the Main Body ECU which will then do it’s thing to unlock the door.
That’s about all there is to this system.
What You Need
Don’t bother with Radio Shack, they no longer carry them. You can purchase this online from All Electronics, 2 for $1.00. Here’s a link to the reed switch I have used on all my vehicle for years.
How much wire you will need will depend on where you decide to hide your reed switch.
To help you estimate how much wire you will need, it has to go from the drivers side kick panel inside your cab, to wherever you want to hid the reed switch outside.
Oh heck, just get 20 feet.
I like to use automotive grade Zip Cord wire for things like this. (Two wires physically connected side by side.
Here is a link to purchase the wire I use. 20 feet for $2.60. If you don’t get this, basically any 22 to 28-gauge wire will work.
Please see PDF File posted a few down for the entire write-up if you have an interest.