Electronic – Disabling the lane change signal feature of a 2014, 2015, 2016, 2017 Corolla


I'm not an engineer or auto mechanic, but I know what a diode is, and I know I need one for my application.

A little background (forgive me). I own a driving school, with a fleet of Toyota Corollas. Like many modern cars, these are equipped with a "lane change turn signal feature"… That is, if you move the signal switch only part-way, it will continue to blink 3 times after you release it. This confuses the heck out of our students, who attempt to cancel a signal but if they move it a little too far they see it still blinking, try to move it the other way, then the other way, etc. I dislike the feature myself as it's never proper to blink only 3 times. So, I'd like to disable the feature.

To figure things out, I bought a used turn signal switch matching this model and put it on my multi-meter. So I know which pins are connected as the switch arm is moved. As shown in my graphic, the car sees a connection to GROUND when the switch is moved either left or right, BEFORE it "clicks in". Then when it "clicks into position", it sees another connection… just one wire representing both sides. When the turn signal is turned off after this wire shows a closed circuit, it does NOT keep blinking.

So I'd like the switch to "lie" to the car, telling it that it's "fully clicked" whenever it's moved at all. I don't want to tear the switch apart or even remove it since it's inside the steering column, but the cable is easy to access. It seems I need to add two diodes, shown below in brown.

I've got room to put pretty much any diode between spliced wires, but the only diodes I've worked with are tiny ones on circuit boards.

Any suggestions for where I can find a diode and be reasonably confident it will work? I know almost nothing about diode specs. (Or is my theory completely flawed somehow?)

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Best Answer

FakeMoustache actually should get credit for answering my question, but he posted it as a comment and an answer should be posted here.

[Edit 12/5/2018: I have now done this successfully with three Corollas. Works great!]

Just in case someone has a 2014, 2015, 2016, or 2017 Corolla, below is what I provided to the mechanic to make this simple modification. Even as an experienced driver, I don't like the lane change feature. As FakeMoustache stated, use any of diodes 1N4001, 1N4002 through 1N4007. I used 1N4007's, but probably should have used 1N4001's since the leads are thinner and easier to work with.

Notice the black wire doesn't necessarily have to be cut, but I find it easier than stripping and splicing mid-wire.

Also notice there are two pink wires. Don't splice into the wrong one! See the illustration.

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My work is a bit sloppy but it works.  For this car I would have been better off with IN4401's which have smaller leads. Make sure you insulate.