Prius Mini-Scanner User Manual

Applies to Firmware Version 0.60 (
(Version 0.51 lacks the Compress display method and three data items)

This is the Home page of the User Manual for the Prius Mini-Scanner.  The manual is up-to-date with respect to the stated firmware release.  If you are running an older version of the firmware, some of the functionality described may be unavailable or accessed in a different way.  Instructions for installing the Mini-Scanner, downloading firmware versions and updating the firmware are published separately.

NEW! - User Contributions (converted to PDF)

Turning the Mini-Scanner On and Off

To turn the Mini-Scanner on, press the On/Reset button on the top of the main unit at the very left.  It will display a start-up message and attempt to establish communication with the car.  If this succeeds, the scanner will begin displaying data retrieved from the car.  If it fails, for example the car is not turned on, it will display a diagnostic message and turn itself off.

When the car is turned off, the Mini-Scanner loses communication with the car.  This will cause it to display a message and turn itself off.  Thus, it is safe to leave the Mini-Scanner plugged into the car.  Pressing the On/Reset button while the scanner is on will reset the unit and it will behave as if it was just turned on.  To turn the scanner off without turning off the car, press the Left, Middle and Right buttons at the same time.

Special Options when Turning On or Resetting

If you hold the Left button down while turning on or resetting the Mini-Scanner, the display backlight will come on.  Otherwise, the display backlight will be off.  To turn the backlight on and off while the Mini-Scanner is running, see Options.

Saving of Selections

Most of the selections you make to configure the Mini-Scanner to your liking are saved when it turns off and restored when it is next turned on.  Unless noted otherwise, all the selections you make in Options mode are saved.  Also, all the Favorites slots are saved.  The Display slot, however, is not saved, so you can use this to browse data items without worrying about getting back to where you started.  When the Mini-Scanner turns on, the Display slot is copied from Favorite slot 7 (in firmware versions prior to 0.50, this used to be slot 1).  If you reset the Mini-Scanner, changes to settings are not saved.  So, if you want to discard settings changes, just reset the Mini-Scanner before it turns off.

Control Buttons

The operation of the Mini-Scanner is controlled by three buttons: Left, Middle and Right.  Although these buttons do different things according to what the Mini-Scanner is currently doing, each has certain common functions which help you remember how to operate the unit.

Note: To "tap" a button, press it only briefly.  To "hold" a button, press it and hold it down for one second or more then release it.

Modes of Operation

The mini-scanner has several modes of operation:

The scanner always powers up in Display mode and returns to this mode on a reset.  To cycle through the modes in the order listed above, tap the Middle button.  To return to Display mode from any other mode, hold the Middle button.  In some modes, the Mini-Scanner returns automatically to Display mode after a period of time in which no buttons are pressed.

Display Mode

In this mode, the scanner periodically retrieves two data items from the car via the OBDII interface and displays them.  Since the display has only 20 characters on each of the two lines, the text of the display may appear somewhat terse and cryptic until you get used to it.  All of the items that you can display are fully described in a separate document.

Here is an example of the display:

Battery SoC: 57.5 %
Engine: 1535.25 rpm

The data items that are displayed can be chosen individually in the Select Line modes.  The two items can be saved and recalled as a pair in Favorites mode.  The Right button in Display mode gives you some control over logging to the serial port, which is described later (or go directly to the separate section that describes it).

Favorites Mode

The two data items that you see in Display mode are stored in the Mini-Scanner in a "slot" called the Display slot.  There are seven other slots, in each of which two items can be saved.  These are called "Favorite slots", because you use them to store pairs of data items that you frequently want to see.  In Favorites mode, you can:

To get to Favorites mode from Display mode, tap the Middle button once.  To return to Display mode, hold the Middle button.  If you tap the middle button while in Favorites mode, you will move on to the first Select Line mode.

When you enter Favorites mode, you will be looking at Favorite slot 1.  The Mini-Scanner will briefly tell you this and will then begin to display the values of the data items in this slot.  To move to the next slot, tap the Right button.  To move to the previous slot, tap the Left button.  The slots are arranged in a circle, so if you tap your way up past slot 7 you reappear at slot 1and vice versa.  As you enter each slot, you will breifly see the slot number and then the values of the data items in that slot.  It is not necessary to wait for the items to appear before you move to the next slot.  If you leave the Mini-Scanner in Favorites mode, it will behave just as it does in Display mode except that it will retrieve from the vehicle and display the data items in the selected Favorite slot instead of the Display slot.  In one way, this is most convenient as you can set up the slots with the data items that most interest you and move among them at will.  However, it can also be a little confusing because what happens when you use the buttons is different in Display and Favorites mode.  There is no difference in the display between Favorites and Display modes.  If you lose track of which mode you're in, hold the Middle button to make sure you are in Display mode.

To choose the two data items to be stored in a Favorite slot, you must first select them into the Display slot, see Display mode and Select Line modes.  Then, move to Favorites mode (tap Middle) and find your way to the slot in which you want to store these two items (tap Right and Left).  When you reach the destination slot, hold the Right button.  The data items selected into the Display slot are copied into the current Favorite slot.  The Mini-Scanner returns to Display mode.

As well as storing the Display slot in a selected Favorite slot, you can recall the data items from a Favorite slot to the Display slot.  Go to favorites mode, find the slot and hold the Left button.  The data items stored in the Favorite slot are copied into the Display slot.  The Mini-Scanner returns to Display mode.

The previous two paragraphs, in conjunction with knowing how to use the other Mini-Scanner modes, contain the information you need to set up the Favorite slots to your liking.  But, it has to be admitted that when you put these instructions into practice it is quite easy to get lost.  Let's try to explain it another way.  In Favorites mode, you choose the slot you want to work with by tapping Right and Left.  You can leave the buttons alone and use the slot just like the Display slot.  You can hold the Left button, which will copy the data items from this Favorite slot to the Display slot and go to Display mode.  You can hold the Right button, which will copy the data items the other way, from the Display slot to the Favorite slot, and also go to Display mode.  This last is how you get items into Favorite slots in the first place, so let's go over that in more detail.  From Display mode, tap Middle twice to go past Favorites mode into Select Line One mode.  Pick the first item for your slot by tapping Right and Left.  Tap Middle once to go to Select Line Two mode.  Pick the second item.  Now, hold Middle to get quickly back to Display mode.  Tap Middle just once this time to get into Favorites mode.  Tap Right and Left to find the slot you want to set.  Once there, hold Right.  The slot is set with the data items you selected to Display mode.  When you follow this procedure, it is a good idea to have a plan in mind and to have it written down.  When you're done, browse the Favorite slots to make sure you've got what you want.

Select Line Modes

There is a Select Line mode for each display line.  When you enter the first Select Line mode, you are able to select the data item that will appear on the first (top) line of the Display.  When you advance to the next Select Line mode, you can select the item to appear on the next (bottom) line of the Display.  When you are in a Select Line mode, the first character of the selectable display line shows a distinctive flashing block cursor.  To return to Display mode after making selections, hold the middle button.

In a Select Line mode, tapping the Right button cycles forwards through the list of available data items.  Tapping the Left button cycles backwards.  The list is circular, so if you tap your way out of the bottom you reappear at the top and vice versa.  As soon as you tap the button, the "format" text of the item appears on the appropriate line of the display.  This is the description of the item that will appear in Display mode, but with the numerical value replaced by placeholder characters.  The intent is that from this format text you will be able to recognize the item and either accept the selection or continue to the next item.  For example, when you select the traction battery state-of-charge item, you will see this: "Battery SoC: ||`| %".  The placeholder characters will be replaced by the actual value obtained from the car as soon as the Mini-Scanner refreshes the display line.  This may be almost immediately or after a brief delay, depending on exactly when you tap the button and how fast items are being refreshed.  This means that you can inspect the current value of each data item in turn without returning to Display mode.

The items you select for display are presently not saved when the Mini-Scanner turns off.  You must make the selection each time the Mini-Scanner is turned on or reset.

Options Mode

In this mode, the Mini-Scanner allows you to set various options.  Details of the options themselves are given in a separate section of the User Manual.  Here, we describe the general mechanism of choosing options.

Upon entering this mode, the mode announcement will display for a short time.  Then, the first option will be presented.  The top line of the display shows the option name, for example "Items to Request/Log".  The bottom line of the display shows the available choices for that option, for example "  [2] 3  4  5  6    ".  The currently selected choice is shown in brackets.  So, the display described above means that the number of items to be requested and logged is 2.

Use the right button to change the selected choice.  Tapping the right button moves the selection forward thought the list of choices.  Holding the button sets the selection to the default choice.  It is not possible to go backwards through the list of choices.  Therefore, options will be arranged to have a small number of choices.  In our example, tapping right twice will change the selected choice to 4 and the bottom line of the display will appear thus:  "   2  3 [4] 5  6    ".

Selecting an option choice does not put that choice into effect.  To do this, hold the left button.  The choice is now effective and the bottom line of the display reads " Option Choice Made ".  In our example, if we hold the left button after tapping right twice, the number of items to be requested and logged will change from 2 to 4.  Some option choices are saved at power-down, but others are lost when the Mini-Scanner turns off.  See the description of the various Options for details.

Tapping the left button moves forwards through the list of options.  The display will show the next option's name on the top line and its list of choices on the bottom line.  It is not possible to move backwards through the list of options.  If you change the selected choice for an option and move to the next option by tapping left, that change of selected choice is lost and if you return to that option the original (and currently effective) choice will be shown.


This example describes how to select the "Fast" request rate on a Mini-Scanner that is currently set for the "Normal" request rate and has just been turned on.

Trouble Codes Mode (new in Version 0.50)

When you enter Trouble Codes mode nothing much happens at first.  By tapping the Right and Left buttons, you can browse forward and back in the list of ECUs with which the Mini-Scanner can communicate.  These ECUs are:

Data items are still being requested and logged.  In order to retrieve Diagnostic Trouble Codes (DTCs) for an ECU, select that ECU (by tapping the Right and Left buttons) and then hold the Right button.  The result will appear on the bottom line of the display after a short pause.  The requesting and logging of data items will stop.  This is because the Mini-Scanner has to enter into a different mode of communication with the ECUs to retrieve the DTCs.  If you accidentally enter Trouble Codes mode while logging, you will not lose any information as long as you don't hold either the Right or Left buttons.  You can just leave this mode by tapping or holding the Middle button.

Once you have started the retrieval of DTCs by holding the Right button, the information is refreshed at intervals of about one second.  So, if a Trouble Code arises, you will see it on the display.  If you tap the Right or Left buttons to select a different ECU, DTCs will then be retrieved from that ECU and displayed.  So, you can browse through the ECUs inspecting their DTCs in turn.

The display shows three DTCs, each consisting of a prefix letter and four digits.  The code P0000 means that there is no Trouble Code, so when there are no DTCs in an ECU you will see " P0000 P0000 P0000  ".  If you have one DTC, it will appear in the first position.  For example, if you remove the Service Plug from the high voltage battery and turn the car on, the Hybrid Vehicle ECU will show " P3140 P0000 P0000  ".  The code P3140 means "Interlock Malfunction" and can be looked up in the Diagnostic Repair Manual.

When you leave Trouble Codes mode (by tapping or holding the Middle button), if you started the retrieval of DTCs then the Mini-Scanner has to get back to the mode of communication in which it can talk to all the ECUs and get data items.  To do this, it will repeat the ISO9141 slow initialization that it did when you turned it on.  After a few seconds, if you go back to Display mode, the display and logging of data items will resume.  Changed settings have not been stored and the Display mode slots are as you left them.  The slow initialization is purely to get back in touch with all the ECUs.

In Trouble Codes mode it is possible to clear DTCs as well as display them.  In general, this is not a good idea as your service department may need this information to diagnose problems with your car.  Therefore, to clear DTCs, the Mini-Scanner makes you jump through a few hoops.  First, you must have Clearing Trouble Codes enabled in the Options mode.  Refer to the section on Options for how to do this.  Now, select the ECU in which you want to clear DTCs by tapping the Right and Left buttons as before.  It doesn't matter if you are retrieving DTCs or not, this will be started when you clear the DTCs.  Hold the Left button.  A message will appear asking you if you really want to clear the DTCs.  (If Clearing Trouble Codes is not enabled in the Options mode, you will be informed of this instead.)  If you decide to continue and clear the DTCs, hold the Left button again.  The DTCs will be cleared and the Mini-Scanner will begin retrieving the DTCs from that ECU, which naturally will all be P0000.  If you change your mind about clearing DTCs, any button action other than holding the Left button will cancel the request.

Diagnostic Trouble Codes Listing

A Mini-Scanner owner has very kindly transcribed the Prius DTCs from the repair manual and sent them to me.  You can find them here.

DTCs and the Battery ECU

One of the data items you can get from the Battery ECU is the number of DTCs.  I have no idea why this number gets to be so large and yet retrieving DTCs in Trouble Codes mode gets you nothing but P0000.  However, clearing DTCs in the Battery ECU sets the number to zero ... until you drive the car again.  Also, clearing DTCs in the Battery ECU sets the Ignition Off Hours item to zero.  It then begins to form a new average of how long you leave the car turned off.

Logging via the Serial Port

Data retrieved from the vehicle by the Mini-Scanner can be sent to a computer via the serial port.  This is described in detail in a separate section of the User Manual.

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Last edited December 5, 2003.  All material Copyright   2003 Graham Davies.  No liability accepted.