The default setting is "Intermittent" but it can be changed to "Single" but not turned off. Even changing to "Single" needs to be done by a dealer or someone with the correct "maintenance device". J
The Android app "Prius Tweak" can do it. You will have to buy an ELM327 OBD2 Bluetooth adapter and pair it with an android phone to work right.
Couldn't find Prius Tweak for Android in Play Store but I did find it here on APKPure: <can't post link but you can google> However, when I installed it and ran it, it said that it was designed for an older Android and so might not run right. In either case, I inserted my OBD2 dongle, ran the app, saw the check box for "Connect", ticked it, and after a while the text at the bottom said Connecting....then Ready. I then checked "Reversing beep" - nothing changed other than the box being checked and I put the car into reverse, and still there were beeps. And I also "unchecked it", put into reverse - still beeping. So, maybe there is something wrong with my OBDII (got a cheap one for 3.95), or maybe Prius Tweak doesn't work under new android. While other apps can show engine RPM, speed, temperature at inlet and some other sensor information, Carista app tells me my "sensor is defective". So, not sure. But yes, it's an "ELM327 OBD2 Bluetooth adapter". I read that there are all sorts of different OBD2 "protocols" out there. Is there an OBD2 bluetooth dongle that someone has tested and it definitely works (preferably with an app that's been updated)?
A ScanGauge is another means of changing the beep to a single backup beep. I have a ScanGauge in my PriusV. Mine is mounted on the steering column. If you are not familiar with ScanGauge, it comes with a cable that plugs into the OBDII port of your car and displays 4 parameters at a time on an LCD display. You can select which 4 parameters from a list of about 120 parameters. These parameters are for all makes and models of vehicles so not all 120 parameters are valid for every vehicle. For example, some of the parameters are related to a diesel engine. I chose Engine RPM, Water Temperature, Battery Current and MPG to display. There are some parameters specific to the Prius that are not available in those 120 parameters. ScanGauge offers Xgauge capabilities which means that you can add a custom parameter if it is not available among the 120 generic parameters. Xgauges allow you to enter codes that will retrieve a value or change/set a parameter for a specific vehicle. I searched the Internet and found the PID (parameter ID) codes for disabling the Prius reverse beeper and created an Xgauge for it. While I have it selected as one of the 4 on the display, it constantly sends the command to set the back-up beep to a single beep. I then change that parameter back to the 4 that I normally monitor which are listed above. I believe that disconnecting the 12 volt battery sets these Prius parameters to their default values so the backup beeps would be back. I would have to select my Xgauge to set the beep to single again after reconnecting the battery.
