You can also find an official Toyota TSB on this topic by viewing this PDF.
2003 Keyless Entry System
2003 Keyless Entry System Upgrade Upgrade
By: Randy Hobart
If you have a 2003 Tacoma equipped with the factory Keyless Entry system, this simple tip will upgrade it to a fully functional alarm.
(This tip has only been successfully tested on 2003 models - older models may not have the proper wiring configuration)
When Toyota builds their 2003 Tacoma, the Keyless Entry system is installed with all of the basic components required for the Alarm upgrade. In fact, the only component that needs to be added is the glass-breakage sensor. (This is a small dash-mounted component that also includes an LED warning light)
The glass-breakage sensor and LED are not required for the Alarm to function.
Follow this simple step to convert the Keyless Entry into an Alarm...
(In the photos, the lower dash panel has been removed for clarity - the lower dash panel does not need to be removed to access the wiring)
Under the driver-side dash, just to the left of the steering column, locate a single-pin connector and disconnect it. This connector is taped up to the wiring harness.
Leave the connector disconnected and re-tape it back against the wiring to secure it.
THATS IT! A free Alarm upgrade.
A note about the alarm functionality:
This modification converts your keyless entry system into an alarm that functions the same as the Toyota factory alarm, with the exception of a glass-breakage sensor. The factory alarm is NOT equipped with a motion sensor or a shock sensor. This means that your alarm will trigger only if:
(1) the doors are forcibly or manually unlocked and opened without the key (2) power is disconnected (and then re-connected) from the battery (3) an attempt is made to start the vehicle without the key
Furthermore, if the alarm is triggered, the security system will disable the starter and continually attempt to lock the doors if they are unlocked.
This modification is simply a FREE upgrade. If you are in need of a more sophisticated alarm system, it is recommended that you look into purchasing the actual RS3200 Plus upgrade, or an aftermarket alarm system.
To test the new modified alarm, perform the following:
Roll down the driver side window.
Activate the alarm by
Press the power lock button in the door, then close the door, OR Close the door, then lock the doors from the outside with the key, OR Close the door, then press the LOCK button on the transmitter.
Wait 30 Seconds for the alarm to activate.
Reach in through the window to unlock and open the door.
The alarm should trigger.
To deactivate:
Press the UNLOCK button on the transmitter, OR Unlock the door with the key, OR
Insert the key into the ignition and turn it to ON.
To go one step further, an aftermarket LED light may be added. (Or, the factory LED can be purchased separately; Toyota part number 08192-3T820)
The lower dash panel will have to be removed to access the proper wiring.
In the first picture above, you will see a wire harness that T's at the base of the steering column and folds back to the left. The loose end of that wire harness is taped up. Pull the end out where you can access the unused 4-pin connector. This connector is where the LED/glass sensor gets plugged in.
There are 4 wires, a black, a white, and 2 colored wires. The 2 colored wires are used for the LED.
You can splice into these 2 wires to connect an LED. (The black and white wires are for the sensor) 8/26/07
User onelowrx7 suggested that the Toyota LED/Glass breakage sensor could be installed in the hazard light button location. Here are his notes on installing the sensor and relocating the hazzard lights button:
The information found in your DIY Alarm Upgrade worked out great for me! Except I wanted to take it the one step further as explained. I wanted the Toyota Factory L.E.D. / Glass Break Sensor installed to complete the alarm system. Here is how I did it:
I ordered the part listed above (Toyota part number 08192-3T820) and when it arrived I noticed that its OEM connectors were intact but the wiring was quite short (about 3 inches). I decided that since my particular model came with the Rear Differential Lock Switch and the Clutch Start Cancel Switch that the best location would be where the factory Hazard switch was located. I would have to relocate the Hazard switch to one of the blanks located at the bottom of the dash next to the additional 120v power outlets.
Note: if you do not have the Rear Diff Lock Switch or the Clutch Start Cancel switch, you could place the factory LED there. The stock wiring was long enough although the connectors were all Male/Male therefore, you would have to have splice your own no matter where you decide.
First, locate the wire that will control the LED / GB Sensor...
(Where the dotted line is – should be about where the wire ends up)
Next, un-tape the wire so that it can be relocated to your desired location. Run the unwrapped wire up to the hazzard button's srcinal location.
Let’s start with the LED harness since that’s the main goal here. First as the guide above stated, there are 4 wires. 2 that go the Glass Break Sensor (these are white and black).
The other 2 are for the LED (the guide stated “colored”, mine were WHITE w/ BLACK stripe and RED, be careful when re-connecting these).
Those factory harnesses both on the car side and on the switch side now need to be cut.
They both are male connectors and won’t mate. I chose quick connects, but you can use butt connectors if you like.
Note: If you're simply placing this switch in a blank location near the steering wheel (where my diff lock switch or clutch cancel switch is), you're almost done!
Now on to the Hazard switch. The wiring is only made to go to one location, but with some butt connectors, a striper, a crimper, and some extra wire, it can go wherever you like! I chose speaker wire because it was the right gauge and it actually worked out great. Cut the harness with a couple inches of lead, and then strip the factory wires and attach your extra lengths.
You’ll need to thread the wiring down to the bottom of the console - this is pretty easy. I recommend only wiring one wire at a time; there are a total of 8 wires in the hazard switch harness.
I went slowly and still made a mistake, I wired two colors backwards. The result was a hazard switch AND turn signals that didn’t work. After checking the fuses, I went back and looked over my wiring and found the culprit. I added some electrical tape spiraled around the wiring just to clean things up a bit. Here's the finished product: