Auto-Dimming Dash Light Mod 5th Gen 4Runner – How To Dim The Lights in Your 4Runner

Sometimes, a mod isn’t about improving stock capabilities; it’s about bringing your vehicle up to what should be stock. In this case, that’s unlocking your 4Runner’s ability to do something it’s already built and programmed to do. Certain 5th Gen 4Runners are pre-wired for auto-dimming lighting. Specifically, dimming the dash and infotainment touchscreen in a dark environment, or increasing brightness in a sunny one. For TRD Pro or Limited models, that feature is active as soon as you take delivery of your vehicle.

But for the rest of us, we have to switch between Off and Daytime Running Lights in bright environments, and On in dark ones. Not a big deal, but easy enough to fix if you’re willing to roll the dice with international sellers on Amazon or eBay.

Find It Online 

• Auto Light Control Sensor (Toyota part#89121-50020): Check Price

Note that when I ordered my sensor, it shipped from China using China Post. If you don’t have any experience with China Post, that means it took approximately 6 weeks from purchase to delivery.

You can, of course, buy the part directly from Toyota. But doing so will cost you $200 compared to the $10-$15 you can spend if you’re willing to take the gamble on sketchy Chinese sellers on Amazon or eBay. But more on that in a minute.

Tools & Materials

It doesn’t get much easier than this.

• Interior Trim Tool
• Something to clean your windshield afterward (optional)

Check to Make Sure You’re Compatible

A fair bit of research has led me to believe that the only models pre-wired for this sensor are the SR5 Premium, the TRD Off-Road Premium, the TRD Pro, and the Limited. In other words, it is models with the upgraded infotainment system, and the Pro and Limited models already have the sensor installed from the factory, so that they won’t benefit from this mod. So if you have either variety of Premium models, read on.

But if you don’t, it’s easy enough to check by popping off the dash plug and taking a look. Slip your trim tool under the blank plug at the center of your dash, and pop it out. If there’s a wire connected to the plug, you’re in the game. If not, better luck next time.

Step 1. Remove Blank Plug

Just like step zero, all you’ve got to do is slip your trim tool in between the blank plug and your dash and use the power of leverage to pop it up. If your 4Runner is pre-wired, the connector will be attached to the plug.

Step 2. Swap on the Sensor & Install

Carefully, so you don’t drop the wire back behind the dash, disconnect the wiring, and attach it to your sensor.

Feed the wires into the hole, then pop the Sensor back in. Note: This part of the process appears to be irreversible, so do not “test fit” the sensor before attaching it to the wiring harness.

Testing

That should be it. Start your 4Runner, turn on your headlights, and test the sensor by either adding light (with your phone flashlight) or blocking it (by covering the sensor with your hand). When the sensor detects light, it should brighten both your infotainment screen and your dashboard illumination to the same levels you have when in Daytime Running Lights or Off. When the sensor doesn’t detect light, it will dim both to the settings you previously had for On.

Final Thoughts

The sensor’s functionality is exactly what it’s supposed to be. It’s especially useful if you like your interior extra-dark at night but still want more visible instruments when your headlights are on during heavy rain or snow. Not exactly a game-changing mod, but it’s nice not have to switch between headlight settings while driving in variable weather. It’s a feature that came standard on my wife’s fifteen-year-old Corolla, but Toyota makes you DIY for a much newer 4Runner. Weird.

So I’m left wondering why I had to do it in the first place. Not that I actually needed to, obviously. But why is Toyota not doing it at the factory? My 4Runner had everything it needed to run this sensor. Toyota even wired a dummy plug, so it’s not like they saved on installation costs. Their $200 parts price is obviously inflated, even if the back-door prices on Amazon and eBay are artificially low. But in the cost of a $40,000 truck, it seems bizarre that Toyota isn’t willing to throw in the sensor.