2006 Prius Voice Recognition Problems


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Updated January 18th, 2006

Introduction:

A number of recent 2006 Prius owners have posted messages on the PriusChat discussion site about their limited success in using the voice recognition system which controls the navigation system and other functions.

Personally, I find that the system recognizes my commands most of the time, but that the error rate is way too high to allow the voice system to be useful or reliable.

I believe I have found a lead which may point to the cause of the problem. In summary, I think that the audio levels coming from the microphone are not reaching the navigation computer with the proper gain. This document shows how to check your own audio levels on a 2006 prius and decide for yourself if there is a hardware problem.

Warning:

The following instructions show how to access the internal service menus of your Prius. These menus are largely undocumented and care should be taken not to change any values. The author assumes no liability for problems which you may experience as a result of using these menus. Perform the following tests only when the vehicle is safely parked.

You will not be able to exit from the following menus without turning off Prius and restarting it.

Accessing the Menus:

On your MFD, press the "Display" button. The Display/Brightness/Contrast overlay will appear.

As indicated in the photo below, press the "secret" buttons just within boundaries of the display pop-up. Press in the following order: Top - Bottom - Top - Bottom - Top - Bottom; six presses total.

You should now be at a screen called "System Check Mode". From there, press "Menu", and you should wind up at the Diagnosis Menu:

Performing the 1st Test:

From the Diagnosis Menu, touch "Display Check" and then on "Mic & Voice Recognition":

The audio from the Prius microphone (located in the cluster containing your dome light and map lights) is sent to at least two destinations, the MFD, and the navigation system. Here, we are testing the audio levels which are reaching the MFD.

Here, you can speak some phrases and see the audio level bars light up...

Using the Record and Play buttons, you can record about 5 seconds of audio and then hear it back, basically hearing what the car "hears". From this screen, you should hear a reasonably clear version of what you have recorded. This is the audio that goes to the MFD.

Practice a phrase or hum a sustained tone that reliably lights up 4 bars on the meter. When played back, the recorded audio should be free of distortion. Be sure you can achieve this predictably, as you will need to make the same sound again in another menu for comparison purposes.

After you are done with this test screen, press "Disp Menu" in the upper right corner to return to the previous screen, and then "Menu" in the upper right corner to return to the Diagnosis Menu.

Performing the 2nd Test:

From the Diagnosis Menu, touch "Navigation Check" to go to the Navigation Menu. From there, click on "Mic & Voice Recognition Check":

You will arrive at an audio meter screen which is very similar (but not exactly the same!) as the one used in the first test. This is the meter which monitors the audio level reaching the navigation system.

Perform your recording and playback test again... try to repeat your phrases which you previously learned would achieve 4 bars of audio level. Note that in this menu, the same phrase (at least on my Prius) will only reach 2 bars of audio level, and sounds very weak during playback.

Now try talking louder, try to get 4 or 5 bars of audio. You can even get the bars into the red, but you will have to shout. But note that even the audio with 3 and 4 bars of green on this menu sounds clipped and heavily distorted!

It appears that the navigation system is expecting an audio level over a broad range, but that the audio arriving at the system does not cover that full range. Further, any attempt to talk very loudly to compensate for the low levels results in distortion.

I theorize that the voice recognition system, as designed, is fairly reliable. It appears that it is recognizing commands from a very low input signal. But when you add road noise or slightly soft speech, it doesn't have much to go on. Talking too loudly causes the signal reaching the voice system to become so distorted that it can't understand what is being said.

Keeping in touch...

I would be interested in hearing the results from those of you who have completed the test. Please write to bob (at) peak dot org. If you reproduce this problem for a dealer service technician, please let me know what you were told.

As I gather new information or learn of any statements from Toyota, I will post updates here.

Happy hunting,
Bob Richardson