Prius Mini-OBDII Scanner - User Manual

This is a draft User Manual for the Prius Mini-Scanner.  This does not bind me to implementing the features described.  I am publishing it for review and critical comment.  Please bear in mind that I'm trying to keep the cost down while putting a little something in my pocket to reward me for the considerable effort of creating this thing.  I'm sure you want four items, not two, and a big graphical display instead of a little text one, but I really can't do that for $100 within the scope of this project.  Maybe if thousands of people want one of these ...

The final user manual will include all of the Mini-Scanner's capabilities, for example a list of supported PIDs.  I will keep the current version posted so people who fall behind with software updates will need to download the manual for their version.  Or maybe I will archive old versions.  Yes, probably that.

Installation

The Mini-Scanner consists of three parts: the DLC adapter, the main unit and a flat ribbon cable.  Plug the cable into the main unit.  Mount the main unit behind the steering wheel or in some other location of your choice.  The cable should fit behind the tiltable steering wheel assembly and drop down into the footwell.  Thus, it can be concealed without any disassembly of the car.  Plug the cable into the DLC adapter.  Plug the DLC adapter into the DLC.  Tie up any loose cable.

Power On/Off

Press the Power button on the main unit to turn it ON.  It will display a start-up message and attempt to establish communication with the car.  If this succeeds, the scanner will begin displaying the items selected as "favorite" in slot zero (see below).  If it fails, for example the car is not turned ON, it will retry every ten seconds for one minute.  If the scanner cannot establish communication with the car for one minute, it will turn itself OFF.  When the car is turned OFF, the scanner loses communication and as described above, this will cause it to turn itself OFF.  Thus, it is safe to leave the scanner plugged in.  Pressing the Power button while the scanner is ON will reset the scanner and it will behave as if it was just turned ON.  To turn the scanner OFF without turning OFF the car, <TBD - is this necessary?>

Modes of Operation

The operation of the mini-scanner is controlled by three buttons: Left, Middle (also "Mode") and Right (also "Reset").  The right button in some cases resets a selection, but does not reset the scanner.  To reset the scanner, press the Power button.

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.

The mini-scanner has eight modes of operation: Display, Select Favorites, Select Top Line, Select Bottom Line, Trouble Codes, Options, Custom and Reflash.  The scanner always powers up in Display mode and returns to this mode on a reset.  To cycle through the modes in the ordered listed above, tap the Middle/Mode button.  To return to Display mode, hold the Middle/Mode button.  The scanner automatically returns to Display mode if no buttons are pressed for ten seconds.

Display Mode

In this mode, the scanner periodically retrieves two data items from the car via the OBDII interface, displays them and sends them out of the serial port for external logging.  Here are some examples of the display (two lines of 20 characters each):

If the Left button is tapped in this mode, the scanner enters the History sub-mode.  Data is not retrieved from the car and instead a value is shown from the 60 seconds of operation before entering this sub-mode.  Each tap of the Left button steps backwards in time by 5 seconds until 60 seconds is reached.  Holding the Left button jumps to 60 seconds.  Each tap of the Right button steps forwards in time by 1 second until zero seconds is reached.  Holding the Right button replays saved data from the displayed time to the end.

If the Right button is taped in this mode, any calculated value being displayed is reset.  For example, if you are displaying cumulative battery use the accumulated value is cleared to zero.

Select Favorites Mode

In this mode, the scanner allows you to select one of a number of "favorite" pairs of data items for the Display mode.  Tapping the Right button cycles forwards through the favorite "slots".  Tapping the Left button cycles backwards.  Holding the Left button replaces the contents of the displayed favorite slot with the pair of items currently configured for the Display mode.  Holding the Right button clears the currently displayed favorite slot.  There are ten available slots for favorites, numbered zero through nine.  On power-up or Reset, the scanner displays favorite slot zero.  If this slot is empty, the scanner idles.  Here are some example displays in Favorites mode:

Select Top Line Mode

In this mode, the scanner allows you to select a particular data item for the top line in the Display mode.  Tapping the Right button cycles forwards through the available items.  Tapping the Left button cycles backwards.  Holding the buttons jumps through the items in blocks and can be used to get to an item more quickly when you have an ordered listing available.  When you leave this mode, either tapping Middle to go to another mode, holding Middle to return to the Display mode or allowing the scanner to time-out and return to the Display mode, the item shown on the top line becomes the item displayed on that line.

Select Bottom Line Mode

In this mode, the scanner allows you to select a particular data item for the bottom line in the Display mode.  Operation is otherwise identical to the Select Top Line Mode, see above. Here are some example displays in Select Top Line and Select Bottom Line modes:

Trouble Codes Mode

In this mode, the scanner allows you to retrieve any trouble codes stored in the car.  Note that the Prius Mini-Scanner is not intended to be a fully-functional diagnostic tool and if you intend to regularly diagnose and repair problems with your car you would be better off with a more expensive stand-alone or computer-based scanner.  However, with the Mini-Scanner, you can find out what codes are stored and what they mean.  This may help you decide whether to visit the dealer's repair shop and to check that you are being dealt with honestly.

Tapping the Left button in this mode starts the process of retrieving trouble codes from the car.  When this is complete, the display shows the number of trouble codes and whether the MIL (malfunction indicator lamp) is commanded ON.  Tapping the Right button displays a more verbose explanation of each trouble code in turn.  Holding both Left and Right buttons clears the trouble codes if the option to do this is set appropriately.  In general, you should not clear trouble codes as it destroys information that is useful to a dealer in repairing problems with your car.

Options Mode

In this mode, the scanner allows you to set various options. The display looks like this (the star indicates that the value has been changed and awaits confirmation):

A list of possible options (default in bold) is:

• number of display lines - 2 or 4 (for support of extra-cost 4-line display)
• update rate - slow, medium, fast (higher rates may interfere with car's operation)
• units - USA, metric, UK (kph vs mph, how big are gallons, etc.)
• powerdown delay - 1, 3, 10, 30 minutes
• use buttons while moving - disabled, enabled (for safety, may go back to default on reset and power cycle)
• clear trouble codes - disabled, enabled (advanced feature, reverts to disabled on power cycle or reset)

Tapping the Left button cycles through the options.  Tapping the Right button cycles through the possible values of the currently selected option.  Holding the Left button sets the current option to the current value.  Holding the Right button resets the current option to its default value.

Reviewer suggestion - Options disabled on reset should be towards the top of the option list and maybe options should be higher in the mode cycle to reduce programming effort at startup.

Clarification - Update rates are TBD, largely because a high rate might interfere with the car due to load on the ECUs.  The network load isn't much of an issue as the network is only used for diagnostic data and is normally idle.  As a starting point, slow might be every two seconds, comparable to the multi-information display, medium might be once per second and fast twice per second.

Custom Mode

In this mode, the scanner allows you to set up custom messages to be sent to the car.  The message is specified as a series of octets (bytes) in hexadecimal notation.  The car's response is displayed in the same way.  The display scrolls if the response  is longer than will fit on the display (14 octets for a two-line by 20 character display).  <How to set up messages is TBD, may be too tedious to be useful>

Reflash Mode

In this mode, the scanner allows you to replace the software using an external computer and an optional adapter.  Tapping the Left button and then Holding both Left and Right buttons starts the reflash process.  No other button actions have any effect in this mode.

It is preferable not to interrupt the reflash process once it has begun, for example by disconnecting the computer or removing power.  If this happens, the scanner may become inoperable and will have to be returned for repair (although I will try to arrange for this not to happen).