With CAN-View, you have the ability to view Prius engineering parameters in real time that previously were available only through an expensive, highly specialized, PC based Toyota Scan Tool.
Jim K. - CleanMPG
- July 12, 2007
For all the technical sophistication of the Toyota Prius, its factory instrumentation doesn’t tell you much about the goings-on under the hood. For Prius owners who really want to know what’s happening in real time when they press the go-pedal, Can-View meets the need.
is an aftermarket device for the Prius-II (NHW20 model) that taps into the car’s CAN bus. CAN stands for controller area network
. It is a method by which a vehicle’s electronic control units communicate data. CAN data in the Prius can be accessed via the vehicle’s OBD-II
Several configurations of CV are available, depending on the model year of the car and whether it has factory NAV. The version for 2004 & 2005 models (V3) displays CAN data on the multi-function display (MFD). Later Prius models lack an RGB input on the MFD for CV to use, and therefore use a different version (V4) that requires an external monitor, purchased separately. CV allows external video feeds, such as a backup camera or aftermarket NAV system, to integrate into the MFD. An optional serial adapter allows data output through an RS232 connector for real-time data logging on a PC. With that option is a connector wire for EV mode. (More on that below.)
In addition to displaying real-time operational data, CV also shows diagnostic trouble codes (DTCs) and various reset-able trip readings.
CV was invented, and in 2005 first was offered for sale, by a hobbyist who desired more instrumentation in his own Prius. A small niche market developed for the device, but to serve the market never became economical for the inventor. Consequently, he announced in May 2007 that the basic model would be discontinued. Instead he is partnering with CalCars
and concentrating on a version to be used as a controller for plug-in conversions. Support for basic models will continue. As of 6/28/07, the CV web site states that about five of the basic versions are still available.
Installation and Setup
Installation approach varies depending on the version. This description is for version 3 for a car without factory NAV. I understand that V3 for factory NAV requires no dash disassembly; it simply taps into the NAV system. See the CV web site
for installation and setup details on all versions.
Installation is fairly straightforward, even for this mechanically challenged individual. It first requires removing several dash panels to gain access to the rear of the MFD and route the cables. I had previously disassembled the dash to install an integrated XM Radio unit, so the prospect of doing so for the CV wasn’t intimidating. I mainly used the dash disassembly described here
for both the XM and CV installations.
All CV cables except the power supply wire are plugin. The power supply wire required tapping into an existing wire behind the MFD. The tap was simple; a wire tap was included with the CV, and the instructions clearly described which wire to use.
Permanent placement of the CV unit itself is somewhat a matter of preference. The unit’s case measures about 5” x 4” x 2”. There are small “nooks and crannies” behind the dash, especially around the glove box, where it might fit. But the two pieces of XM radio hardware already had claimed some of those void spaces. I tried various arrangements (some unworkable) of the CV unit and XM hardware before concluding the best place might simply be in the rather spacious glove box. This provides easy access to connect a serial cable for data logging.
Setup is simple. Several global options can be configured based on user preference, including (but not limited to) audible beeps with screen touches, US measures vs. metric, “nighttime” viewing mode, and auto-saving of minimum and maximum data values and trip parameters. Also available is an adjustment to calibrate CV’s calculated fuel mileage. Setup includes configuring either the CV display or the factory display as the power-up default. Switching between the two is easy and described later. Version 4 has additional setup functions for the external monitor; see here
for more. Specific operational data can be selected for display on individual screens as described below.
Can-View offers numerous data to display and multiple display methods. Operational data are available via graphic screens, numeric only screens, “formatted” screens, an EV parameters screen, trip screens, and a raw CAN data screen. A DTC screen displays codes. This is the main menu from which the data screens are accessed:
This table summarizes what can be seen on which screens:
Most of these are described in some detail on the CV web site
. The visual person (like me) will lean toward these screens. A total of 12 parameters can be displayed graphically via three screens with four parameters apiece. Example:
Bar color changes for data elements whose values can be either positive or negative. In the picture, for example, amperage is red, indicating current flow out of the battery. When flow reverses, the bar turns green.
The large text below each bar shows current values. The small text shows minimum and maximum since the last reset.
The screen button with the small circular icon at the lower left cycles between the three graphic screens.
The button labeled “ICE run” is enabled as a screen button only if the CV EV wire is connected, in which case the screen button becomes an EV switch. Otherwise this is a display item only. Regardless, it displays operating mode as one of:
- ICE run
- ICE spin (as in highway speed coasting or “warp stealth”)
- Stealth (low speed coasting or gliding)
- EV try
- EV mode
- EV deny
- WOT mode (wide open throttle)
“Reset” will reset minimum and maximum values. “Save” saves them, and saves the current screen as the default after the car is powered off. “Menu” returns you to the main menu.
Finally, note the horizontal green bars with “56%” in the middle. Accelerator pedal is represented by the bar on the left, and battery voltage the one on the right (with one bar showing in the photo). As pedal increases or battery voltage drops, these bars expand from their respective borders toward the center and change color from green to yellow to red. The closer the bars move toward the center, the more likely EV mode, if engaged, will be cancelled. The bars have no data values attached to them; they are more qualitative than quantitative. But they are helpful, nonetheless, for a quick look at their relative position. The number between the bars is HV (high voltage) battery state of charge (SOC).
Selecting which data elements to display is simple. There is no need to navigate through several screens to a specific setup menu. Instead, just touch one of the parameters displayed to open another screen that has all available parameters displayed through mostly intuitive icons. Touch the icon of choice to change the parameter and touch “Save” to return to the previous screen.
. These are for folks who want a little more data without graphs. There are two, each with seven parameters available for display. Example:
Like the graphic screens, these are all user configurable.
. These are for the die-hard data geeks. There are two, and they display the most data, 13 on one screen and 11 on the other. They also show minimum and maximum values. Unlike the graphic and numeric screens, they cannot be customized by the user. Example:
Raw CAN data screen
. For the data junkie who also reads CAN-speak, selected raw CAN data packets can be displayed.
. Various trip parameters can be displayed, including distance, time, average MPH, average fuel consumption in gallons (or liters) per hour, average MPG, and percent of ICE run time. A global option allows either auto-saving readings from one trip to the next or clearing them when powering off. The user can also either save or clear them on the fly. Here is the trip screen:
There is a bar-graph screen similar to the Prius factory Consumption screen, but with increments of one mile (maximum of 30) rather than five minutes. The maximum scale value is adjustable on the fly with a screen button, beginning at 8 MPG. Each push of the button doubles the maximum value up to 255. After cycling through all scales, another push displays a text-only reading of one-mile MPG increments for the last 30 miles. Instantaneous and trip MPG readings are displayed in text on both the graphic and text consumption screens.
Finally, sandwiched between the trip screens, though not really containing trip readings, is this screen:
Presumably these are parameters that might be of particular interest to those with the PHEV conversion. Between the displayed data and the throttle and voltage bars at the bottom, this screen actually displays more data elements than any of the graphic or numeric screens. You can cycle between this and the trip screens with the circular arrow button. However, navigating to this and the trip screens from the graphic or numeric screens requires navigating through the main menu and multiple button pushes. The user cannot customize this screen.
Use and Comments
As a visual person, I mainly use the easy-to-see graphic screens while driving.
As I first tried to decide which parameters to monitor, I was like a mosquito in a nudist colony – I didn’t know where to start! So it’s been a trial and error process that will likely continue for awhile. I figured I’d start with some I had become accustomed to monitoring with the ScanGauge, in particular RPM and throttle position, which in CV is more properly called accelerator position; it tracks linearly with accelerator pedal pressure. So I set up one graphic screen with those and two others I figured I would watch regularly: amperage and brake position.
Watching brake position and its relationship to current flow has been an education. I’ve known that crossing the 7 MPH threshold while braking causes a transition from regenerative to mechanical braking. But now I have a constant visual reminder as I see current flow shift at that point from positive to negative. Additionally, I now can see when I’m braking most efficiently, based on pedal value and what I know from Attila Vass’ work
, where he described a value of 17 as achieving the best regenerative braking efficiency.
I set up a second screen to simultaneously monitor RPM, throttle position, and instantaneous MPG, with engine temperature added to check as needed. This might become my primary “pulse and glide” screen. With ScanGauge I used RPM to guide my pulses and, for that matter, all acceleration, aiming to keep RPM at about 2300 or below. I also watched closely the relationship between iMPG and RPM. As I approach the RPM limit during acceleration, I’ve noticed iMPG approaches half the vehicle speed. (I’ve proposed this as a rule of thumb
for those without added instrumentation to use as a guide to efficient acceleration.) More recently after getting Can-View, a PriusChat post
from Ken@Japan caught my attention. He reports that the Japanese hypermilers use pedal position as reported by CAN to gauge their pulses, with best results at a pedal value of 38-40. My observations suggest that the Japanese technique validates the RPM methodology at ~30 MPH and below, which in turn validates the (iMPG > MPH x .05) rule.
I set up the third graphic screen with RPM values for the ICE, MG1, and MG2, and amperage. I expect to monitor these mainly on the highway. I haven’t had much opportunity yet; the upcoming drive to Hybridfest should provide one.
It’s handy to have SOC and the horizontal bar graphs showing throttle and voltage at the bottom of each graphic screen, regardless of which are displayed in the vertical graphs. Though the horizontal graphs do not provide numeric values, they and the SOC reading effectively increase to seven the number of parameters available in the graphic screens.
Navigating between the three graphic screens while driving is easy and can be done without looking. The circular arrow icon used to cycle between screens was intentionally designed in the lower left corner so it can be found by feel as well as by sight.
I use the numeric screens infrequently. I set one up as my “master temperature” screen, with the following temperatures displayed: engine block, engine coolant, HV battery, MG1 windings, MG2 windings, MG1 inverter, and MG2 inverter. The other is an assortment of engine parameters similar to those I have set up on graphics screens, something I can quickly toggle to while checking temperatures. While the numeric screens display more configurable parameters on each than the graphic screens, they lack the always-present horizontal bar graphs and SOC display of the graphic screens. As time goes on, I will probably explore other parameters on these screens, especially those unavailable on the others.
I have used the formatted screen mostly for reviewing maximum and minimum after a driving segment rather than for real-time data monitoring. Though it has the most operational data of any screen, the sheer volume of data makes it cumbersome to use while driving. Finding a particular data element with a quick glance would take some getting used to.
For trip screens, the ScanGauge has a slight edge with its multiple sets. Can-View has just one, though it can be configured either to reset after each drive or to accumulate data for multiple trips. Curiously, trip MPG is displayed only in whole numbers, whereas average fuel flow shows one decimal place and trip distance displays two. A nice feature of the trip data screen is display of ICE-on percentage.
I haven’t made much use of the per-mile consumption history bar chart or tabular screens, glancing at it infrequently mainly out of curiosity. I’m still accustomed to the factory Prius consumption screen.
Speaking of that, switching to the factory screens is simple. Pressing the hard buttons on the outside of the MFD takes you directly to their respective control screens. To return to Can-View, press Info to return to the factory Information screen and then press Info again.
The MFD is apparently hard-coded to switch to the Energy screen when the EV switch is activated in a car so equipped. The CV is supposed to change back to its own screen after a second or two. Sometimes my EV button seemingly misfires (not a CV problem), and because of this screen switching, which includes transient screen “blackouts,” I don't know it has misfired until after I’ve either applied substantial pedal in unrecognized EV mode or burned fuel unnecessarily in unrecognized ICE-on mode. Occasionally after hitting the EV switch the screen fails to cycle back to CV – a small CV bug, it would seem, that I haven’t reported yet.
The display is quite bright, adequate even in direct sunlight. The nighttime driving mode option, activated when the headlights are on, reduces brightness by changing the blue background to black. In addition, with the headlights on, the overall brightness reduces, just like the factory display. But I would prefer the white text and colored bars to be a little dimmer for night driving.
Other comparisons to ScanGauge: I miss the ability to simultaneously monitor the factory screens and add-on instrumentation – a little. It was more of an issue at first, but I’m getting adjusted to the current setup and I’m finding ways to adapt. For example, amperage has quickly become an acceptable replacement for the Energy screen arrows – probably better with its actual data values, into and out of the battery. Beyond that, the volume of Prius-specific data available at my fingertips makes CV worth it. As one might expect, the CV display is much easier to read. Now into my second half-century on this planet, I had to wear reading glasses while driving to see the SG display. Not so with CV. There are a few engine parameters available in SG that CV doesn’t have. The only one I routinely used was engine loading. Again, having Prius-specific data makes it a more than acceptable tradeoff.
There is no CV user guide per se; it would be nice to have one. Instructions for setup and use are available on the CV web site on individual web pages, rather than in a PDF file or other easily downloadable and printable format. Various PriusChat threads provide additional information and tips from other users.
As new features are released, the user can update Can-View code via downloads from the CV website and an external programming module (purchased separately), as described here
. I don’t know if any updates are planned for the basic version, given that it will no longer be sold. However, it would seem reasonable to expect that periodic updates for the PHEV version will continue.
The biggest drawback to Can-View is its price: $389 for my version 3. Version 4 (for 2006 and later models) is $299 but requires the purchase of an external monitor.
I held off buying Can-View for quite awhile – almost too long. It’s too bad the base model is being discontinued. But I’m fortunate to have gotten one of the last available. Strictly as a tool for helping to improve fuel economy, CV's value is questionable; ScanGauge is a more economical option. But the longer I own and drive the Prius, the more I want to learn about how it works. For that, Can-View is a remarkable tool.