Energy & Sustainability Technology
HOW TO – Prius “Stealth mode” mod

01-Tilt
MAKE pal Douglas sent in this awesome Prius “Stealth mode” mod – check it out!Move the steering wheel tilt lever to the unlocked position. Remove the screw which it previously covered…

02-Wheel
Turn the steering wheel 90 degrees right of center. Remove the screw on the right side of the face of the steering column, behind the wheel. Turn the wheel 90 degrees left of center and remove the similar screw on the left side.

03-Column-Right
04-Column-Left
Press inward on the lower half of the plastic steering column cover, just below and forward of the control stalks to disengage the fasteners. Pull gently down; the lower half of the cover should come loose and move down 3-5cm. It requires some wiggling but little force.

05-Connector-Release
Unplug the white connector leading to the turn signal stalk by pressing in on the latch while pulling down.

06-Connector-Cover
Remove the cover from the connector by gently pulling the two retaining tabs outward.

07-Connector
08-Connector-Pin
Remove one of the unused pins from the connector by pressing gently inward on the metal retaining tab with a small sharp object. The pin should slide out easily. Set the pin aside and re-assemble everything else.

09-Dash-Right
Remove the lower glove box using the procedure in the owner’s manual. (See the section which explains how to change the interior air filter.) Remove the vent panel on the far right of the dash by pulling straight toward you; it requires considerable force. Remove the small lower panel by reaching behind it and pushing down on the retaining tabs.

10-Ecm
Remove the vent panel on the far left and one of the two blank switch plates.

11-Dash-Left
Inside the rightmost portion of the dash you should see three ECMs with many wires leading to them. Unplug the lowermost of the four connector plugs from the rightmost ECM (designated H14).

12-Wire-Run
Using a curved wire hanger or similar object, pull two-conductor 24ga. wire from the left side of the dash to the right. Work carefully to avoid damaging factory wiring. Leaving at least 20cm extra on each end, secure the wire to the existing harness or other convenient structure.

13-Switch
Mount a normally-open SPST momentary-contact switch to the blank faceplate, and connect it to the left end of the wire.

14-Groud
Connect one of the conductors on the other end of the wire to any conveninent ground. I used a spade lug under the 10mm screw just left of the ECMs.

15-Connection
Attach the other conductor to the pin removed from the steering column. Test continuity with a multimeter. Though the pin is designed to connect to unstripped wire, I could not get a reliable connection without the proper crimp tool. Stripped wire and a tiny dot of solder did the job. Hold the ECM connector with the wires up and the white retaining strip toward you. Pry the retainer toward you with a small screwdriver; it will only move about 1mm. Insert the new pin, open side toward you, in the second hole from the right on the row closest to you (designated #27). Push it down until the head of the pin is just below the connector housing.

Push the retaining strip back in place. Plug the ECM connector back in, pushing firmly until you hear and feel a click. Verify correct operation then re-assemble the dash. Thanks to Evan Fusco for the documentation I used during this project.

Douglas Henke – henke@insync.net

26 thoughts on “HOW TO – Prius “Stealth mode” mod

  1. Stealth is a special feature of Prius. It’s the ability to drive without the engine running, using only electricity. The result is very smooth movement in total silence. The term “stealth” was coined by owners due to that quietness. This is also sometimes referring to as “stealth mode”.

  2. See:
    http://www.treehugger.com/files/2006/01/hack_your_hybri.php
    Excerpt:
    “Yes folks, as intimate as you might feel with your Prius, your high-tech friend is capable of doing things you never even imagined. With a little do-it-yourself, you can unlock a whole new set of latent magic powers that Toyota never wanted you to know about. The most notable thing your Prius is hiding from you is that it can run on pure EV mode, a feature that comes standard on Asian and European models, but is disengaged on those sent to the US. In “Stealth” mode, a Prius can go up to 34 mph on battery power alone. All the wiring is there–waiting to be hacked. A guide available here via CalCars shows a person how to hack the electronics and install a dashboard EV button using regular old RadioShack parts and household tools.”

  3. > Very nice, but what does it actually *do*?

    Thanks, and good question. (That 500-word limit is _harsh_.)

    The short version is that pressing the EV button is a hint to the power plant that you’d really like to avoid running the gasoline engine (ICE) if at all possible.

    There are a bunch of conditions where the car will refuse to go into electric-only mode (or will leave it if already there). These mostly have to do with protecting the battery, protecting the engine, or obeying some higher-priority pilot^H^H driver command.

    The obvious/common ones are: battery state of charge too low, commanded speed over 34mph, and over-/under-temp readings on various important bits.

    In general, the Prius knows better than you when to use or not use the ICE for best fuel economy. The EV button is for times when you want no ICE for reasons other than milage (like when you need no noise or no exhaust). It is also for times when you know something the car doesn’t (like that you’ll be parking in a couple minutes, or that there’s a big downhill slope just ahead).

    Indiscriminate use of “stealth” mode will reduce your gas milage and may shorten the battery lifetime. (However, Japanese and Euro Prii have this feature from the factory, so I suspect it isn’t that big a risk.)

    A bigger risk is that your dealer might hassle you over warranty service if they see you’ve hax0red your car. While the physical mod can be easily and invisibly reversed, it may leave evidence behind in data logs.

    Disclaimer: Solely at your own risk, author accepts no responsibility, etc.

  4. > Very nice, but what does it actually *do*?

    Thanks, and good question. (That 500-word limit is _harsh_.)

    The short version is that pressing the EV button is a hint to the power plant that you’d really like to avoid running the gasoline engine (ICE) if at all possible.

    There are a bunch of conditions where the car will refuse to go into electric-only mode (or will leave it if already there). These mostly have to do with protecting the battery, protecting the engine, or obeying some higher-priority pilot^H^H driver command.

    The obvious/common ones are: battery state of charge too low, commanded speed over 34mph, and over-/under-temp readings on various important bits.

    In general, the Prius knows better than you when to use or not use the ICE for best fuel economy. The EV button is for times when you want no ICE for reasons other than milage (like when you need no noise or no exhaust). It is also for times when you know something the car doesn’t (like that you’ll be parking in a couple minutes, or that there’s a big downhill slope just ahead).

    Indiscriminate use of “stealth” mode will reduce your gas milage and may shorten the battery lifetime. (However, Japanese and Euro Prii have this feature from the factory, so I suspect it isn’t that big a risk.)

    A bigger risk is that your dealer might hassle you over warranty service if they see you’ve hax0red your car. While the physical mod can be easily and invisibly reversed, it may leave evidence behind in data logs.

    Disclaimer: Solely at your own risk, author accepts no responsibility, etc.

  5. Doug or others,

    A question – is there any visual feedback that you are in stealth mode? Does a message pop up on the energy monitor screen, or anywhere else?
    Does the EV switch light up? Is there any ability to get it to do so, or perhaps an LED indicator somewhere else? Maybe one of the European or Japanese users across the sea can open their Prius up and tell us where the wires from the factory EV switch connect to – there’s probably one for the switch, as illustrated above, and another that runs the light, connected to another pin on the same or a nearby connector.

    Thanks for the great info on the hack.

    Regards,
    aeronaut

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