Vehicle Proximity Notification System Elimination (Sorry Blind People)

There have been quite a few threads started by people wanting to eliminate the proximity warning system: That annoying electronic buzz produced from a speaker mounted in the grill to warn people a hybrid is coming. The issue at hand, however, is that unlike the GenIII, by unplugging this speaker it will throw a fault and a yellow triangle will appear when you start the vehicle advising you to have the proximity sensor checked!

There was at least one thread there someone modified their speaker by breaking it and soldering in some components. There was another thread with someone adding foam in there speaker to silence it. This thread is to show there is a better way.

First a diagram from the service manual referencing the speaker:



So the key is to have resistance between 6.4 and 9.6 ohms to make the system think everything is good.

But what about watts? How do you know what resistor to buy?

I am not an EE but here are the formulas:
There is no direct calculation of ohms to watts. First you need to calculate ampere:

Volt / Ampere = Ohms

The voltage will be Correction Here it is 6volts DC going to speaker not 12volts, for the sake of this I will select 8 ohms so 6/A=8. A = .75
Now that you have ampere you can calculate watts. The formula is:

Volts X Ampere = Watts

So 6 X .75 = Watt. Watt = 4.5
So the perfect way to fake the system is to introduce a 4.5Watt 8Ohm resistor

Now lets get into the hardware. I bought 3 components for this modification:

I originally bought an oversized resistor based on using 12VDC instead of 6VDC. As a result I had to loop back and order the right size to complete this.

However, below are the exact part numbers for the Toyota connector that will plug into the engine harness, and the terminals that plug into the connector. Once the resistor arrives I plan on attaching this to the terminal leads which should complete the build.

I did try this with the oversized resistor and can confirm that there are no warning lights on the dash so it will work.





Picture below is using the oversized resistor.

 

there is a picture of the speaker next to the resistor in this thread. If the resistor needs to be changed I am hoping an EE will chime in. The real key to this thread is that it includes the exact Toyota part number for the connector that mates with the engine harness and the terminals for the connector to allow a speaker bypass.

 

I will take the legal chance-
I measured the voltage at the harness it is 6volts.

So knowing the voltage and the resistance needed the rest of the calculations are as follows:
This will need a 4.5W 8Ohm resistor

 

Update:

After much research I decided to go with the resistor I have. It is vastly oversized at 20W but even in the case where the wattage needed to dissipate is 4.5W, you would typically double that so you would need 10W. The wattage is the amount of energy that the resistor can dissipate without damage. The problem appears to be in using vastly oversized resistors is that the tolerances open up with greater swings. The range being 6.4 - 9.6 Ohms and using an 8 Ohm resistor there is a lot of play here so the tolerances can be vary quite a bit.

As far as heat, after hooking everything up (leaving the resistor exposed rather than with electrical tape), I went on a five minute drive and touched the resistor. As cool as a cucumber so I am quite sure this will be fine.

Finally onto the legal argument of hitting someone and there being a question on if this was working. People, if you hit someone you are screwed. It does not matter if you have a noise maker or not you are not getting out of it. The pedestrian is always right. You are to maintain control of your vehicle at all times. You will never win the argument of "I hit him but the noise maker should have alerted him I was there". Disabling this I suspect could be classified as an equipment violation such as tinting windows darker than the state allows, lowering your car, putting a shaded plate over your license plate etc. The government mandated that > 2012 hybrids need a sound maker, the risk is more not meeting a standard not a way out of running someone over.