This page presents a preliminary listing of the data items that you can display with the Prius Mini-Scanner. For methods of selecting which items to display, see the User Manual. Any items that appear to be available for display but are not described here are unsupported, which means I probably haven't figured out what they are yet.
The "||`|" symbols are placeholders for the actual values. You will see them when a data item is first selected to a display line, but they will then be overwritten with the actual item value retrieved from the vehicle. For example, "Battery SoC: ||`| %" will be replaced with something like "Battery SoC: 57.5 %" when the vehicle responds to a request for the value of the SoC.
The order in which items are listed here corresponds to the order in which they appear in the Mini-Scanner's Select Line modes. I have tried to keep the more interesting items early in the list and also at the very end (since you can go backwards around the list). Until the list stabilizes, a new release may mess up your favorite selections, so you might want to keep a written record of your favorites and check them after uploading new firmware.
Main (traction) battery state of charge (SoC), in percent. Experiments suggest that this percentage is referenced to the full rated capacity of the battery, which is 6.5 ampere.hours.
You can use the SoC value to estimate how "willing" the car will be to run on battery power only. For example, at 60% or higher, you can draw up to about 30 amps from the battery before the engine starts up. At lower SoC, the current at which the engine starts is reduced.
Correlating the indicated SoC with the battery icon on the Energy Monitor display results in some surprises. The table below shows the SoC points at which the icon changes state in the charging and discharging directions. These were determined by independent experiments on US and UK Prius. The EMPTY icon was not seen down to 22% SoC. The maximum SoC achieved was 80%.
|
Charging (Rising SoC) |
Discharging (Falling SoC) |
||
|---|---|---|---|
|
SoC |
Battery Icon |
SoC |
Battery Icon |
|
74.5% -> 75% |
3/4 -> FULL |
72% -> 71.5% |
FULL -> 3/4 |
| 57.5% -> 58% |
1/2 -> 3/4 |
55% -> 54.5% |
3/4 -> 1/2 |
| 44.5% -> 45% |
1/4 -> 1/2 |
42% -> 41.5% |
1/2 -> 1/4 |
|
(not known) |
EMPTY -> 1/4 |
(below 22%) |
1/4 -> EMPTY |
Two things immediately stand out:
The battery icon should therefore be interpreted only as a very rough measure of battery SoC.
Main (traction) battery current, in amperes. The displayed value is positive for charge (current into the battery) and negative for discharge (current out of the battery). You can use this value in conjunction with the battery state of charge to influence whether the car runs on battery power only or starts the engine. In city driving, especially with small hills, you can obtain a noticeable improvement in fuel economy by extending periods of battery only driving and using the engine in a "pulsed" fashion to accelerate and climb hills. You can also use this value to learn a braking strategy that avoids the use of the friction brakes and therefore maximizes the energy recovered by regenerative braking.
Vehicle speed, in kilometers per hour. The Toyota Repair Manual Volume 1 (Diagnostics) says that when the vehicle is stopped the value should be 0 km/hr. How much does that manual cost, again?
Vehicle speed, in miles per hour. Since the ECUs respond to a request for vehicle speed in kilometers per hour, this number is computed by dividing the result by 1.6. This should be accurate enough for Europeans to know by how much they're exceeding the speed limit in the United Kingdom. However, if you're recording speed via the serial port to perform some off-line calculations, it is better to obtain the speed in kilometers per hour and compute the figure in miles per hour yourself, if necessary.
Engine spin rate, in revolutions per minute.
Throttle position sensor output, in percent. Note that the throttle we're talking about here is not the pedal under your right foot, which is the accelerator pedal, but the valve that restricts the flow of air into the engine inlet manifold. The Toyota Repair Manual Volume 1 (Diagnostics) describes this item as "Voltage Output of Throttle Position Sensor Calculated as a percentage". It goes on to say that 0V corresponds to 0% and 5V to 100%. When the throttle is fully closed we should see 0 - 5% and when the throttle is fully open, 90 - 100%. This makes me suspect that I am not scaling the data properly. With my scaling, the rest position of the throttle sensor seems to be at about 15%. I obtained this scaling from Alex Peper's scan tool, which I assume follows the standard for OBD II mandated items such as this one.
Calculated load, in percent. This is a standard OBD-II data item. The Toyota Repair Manual Volume 1 (Diagnostics) describes this as "Calculator Load", but explains that it is the "Current intake air volume as a proportion of max. intake air volume". This makes a lot of sense if you substitute "mass flow rate" for "volume". The manual goes on to say that when idling you can expect a value of 5.4 - 19.2% and when "Racing without load (2,250 rpm)" you should expect 6.9 - 16.2%.
Engine coolant temperature, in degrees Celsius. With city driving in hot weather, my engine temperature rises to 89 °C, which I presume is the point at which the thermostat opens. The Toyota Repair Manual Volume 1 (Diagnostics) describes this as "Engine coolant Temp. Sensor Value" and goes on to say that after warming up you should expect values in the range 80 - 95°C (176 -203°F).
Cylinder one spark timing advance, in degrees of crankshaft rotation. It is very interesting to watch this during the first minute after you start the car. It goes negative, representing a timing retard. The fuel/air mixture is being ignited as the piston descends. Very little energy is extracted, which is why the car runs on battery power at this time (watch the battery current also). So, the exhaust gas remains very hot and quickly heats up the oxygen sensors and catalytic converter to gain control over emissions. The Toyota Repair Manual Volume 1 (Diagnostics) describes this as "Ignition Timing of Cylinder No. 1" and goes on to say that when idling you should expect to see values of "BTDC 7 -15 deg."
Temperature of air flowing into the engine intake manifold, in degrees Celsius. The temperature sensor for this data item is built into the mass air flow sensor (see below). It is not the sensor behind the front bumper that measures ambient air temperature for display on the Multi-Function Display.
Rate of air flow into the engine intake manifold, in grammes per second. Since the emissions control system keeps the fuel to air ratio fairly constant at all times, this air flow is a strong indicator of fuel flow as well. Except, that is, when the engine is spinning without fuel or spark.
MG2 spin rate, in revolutions per minute. Since MG2 is connected to the front wheels of the vehicle via a fixed gear train, there is a simple fixed relationship between the spin rate of MG2 and the vehicle speed. Depending on the rolling radius of your tires, you will see about 58 to 60 r.p.m. at MG2 for each one m.p.h. of vehicle speed. Assuming standard US tires (Potenzas) and nominal inflation for an effective rolling radius of 11.1 inches, the exact ratio from MG2 spin rate to vehicle speed is 6000 (r.p.m.) to 163.27 (km.hr). Although speed always has a positive value, the spin rate of MG2 shows negative when the vehicle moves backwards.
MG2 torque in newton.metres. This needs to be verified, or at least checked. I guessed the scaling of the data by blocking the wheels of my car and watching this figure (scaled) climb to just over 200 before the car surged up onto the blocks. Maybe someone could creep up a hill of known slope on battery power at constant speed.
Note that generally when a motor/generator's spin and torque are in the same direction, it is acting as a motor. When they are in opposite directions, i.e. one is positive and the other negative, it is acting as a generator. The only time that the foregoing is not true is during brief transition periods, for example when the direction of spin is being changed by the application of power.
MG1 spin rate, in revolutions per minute. This is an interesting figure to watch when you're interested in how the Prius manages without having gears to shift. The faster MG1 spins forwards, the faster the engine can spin for a give vehicle speed and the more electrical power can be passed to MG2 to increase the total driving torque. This is how the car simulates a lower mechanical gear. By reducing MG1's spin rate, the vehicle speed increases in relation to the engine spin rate, but less electrical power is available to pass to MG2. This is how the car simulates moving to higher mechanical gears. When the car is up to speed and power demand is low, you will see MG1 reverse direction. Now it is actually taking up power, acting as a motor to increase the vehicle speed relative to the engine spin, putting the car in what amounts to overdrive. This power comes from MG2, which contrary to expectations, now acts as a generator, actually holding the car back. Take a look at MG2 torque while you are cruising and you'll see a negative value.
MG1 torque in newton.metres. This needs to be verified, or at least checked. I guessed the scaling of the data by observing a (scaled) figure of -8 when MG1 was spinning at 4700 r.p.m. and charging the battery at 13 amps with the car stationary. Both mechanical and electrical powers work out to be a bit less than 4 kW.
Actual regenerative braking torque in newton.metres. This needs to be verified. Both this value and the requested regenerative braking torque, below, only move away from zero during braking. However, which is the request and which is actual is guesswork. What I've guessed to be actual has greater resolution than the request and tends to take a lower value than the request when they get over 100. The scaling to newton.metres is, I think, correct as the actual regenerative braking torque tracks the negative torque at MG2 quite closely. Of course, this assumes that the scaling of MG2 torque is correct.
Requested regenerative braking torque in newton.metres. This needs to be verified, see actual regenerative braking torque, above.
The main (traction, high voltage) battery voltage. Although we think of the battery as having 38 modules of six cells at 1.2 volts each for a total nominal voltage of 273.6 volts, don't expect to see this voltage in practice. With not much in the way of charge or discharge current, you are more likely to see something around 300 volts. This will drop when current is drawn from the battery and rise when it is charged. It will also vary with the battery state-of-charge.
The temperature registered by the sensor in MG1's inverter. The inverter is the electronic system that converts the main battery DC power into three-phase AC power to drive the MG as a motor. It also performs the reverse conversion when the MG acts as a generator. Since it is not 100% efficient, lost energy appears as heat, increasing the inverter's temperature. The Prius inverters are water-cooled.
The temperature registered by the sensor in MG2's inverter.
The temperature of MG1 itself.
The temperature of MG2 itself. I recall it was discovered that there are multiple temperature sensors buried in the stator windings of MG2 and this reading is probably some sort of average.
The engine power requested by the Hybrid Vehicle ECU of the Engine ECU. Or so it seems to me.
The engine spin rate requested by the Hybrid Vehicle ECU of the Engine ECU. Or so it seems to me. The actual engine spin rate is usually close to this figure. When engine power is cut off due to low demand but the car is moving at more than 42 m.p.h., the value goes to 1000 r.p.m. So, the Engine ECU does not interpret this figure as a demand to run the engine at that speed using fuel.
This seems to be stuck at zero. If anyone sees anything else, especially if it changes with some identifiable condition, please let me know.
Accelerator pedal main position sensor output, probably in volts. The value typically ranges from 0.6 with no pedal displacement to 3.4 with the pedal pushed all the way to the floor.
Accelerator pedal subordinate position sensor output, probably in volts. The value typically ranges from 1.5 with no pedal displacement to 4.2 with the pedal pushed all the way to the floor.
Shift lever (a.k.a. Mode Selector Lever) position sensor output, probably in volts. Typical values in 'P', 'R', 'N', 'D', and 'B', respectively, are 0.6, 2.9, 3.5, 4.0 and 4.6.
Shift lever (a.k.a. Mode Selector Lever) position sensor output, decoded into a one-hot binary code. The values in 'P', 'R', 'N', 'D', and 'B', respectively, are 1, 2, 4, 8 and 16. When the lever is in between valid positions, the value is zero.
The Toyota Repair Manual Volume 1 (Diagnostics) lists the values of this item thus:
I see values of 0, 1, 2 and 4 most frequently and occasionally I see 3. I think 2 means that the engine is being spun up by the motors prior to applying fuel and spark and 1 means the engine is being forcibly spun down and its kinetic energy returned to the battery.
A Mini-Scanner owner who has paid more attention to this item than I have suggests that 3 means that the engine is running for a reason other than those covered by 4. That is, engine power is not driving the car nor is it being used to generate electrical power. This value is therefore seen during pre-heat (the first phase of engine warmup when the ignition timing is retarded), low-load driving at more than 42 m.p.h. when the engine must spin to protect MG1 and when the engine runs to turn the air-conditioning compressor.
This might be the highest sensor temperature passed to the Hybrid Vehicle ECU by the Battery ECU.
This might be the lowest sensor temperature passed to the Hybrid Vehicle ECU by the Battery ECU.
The Toyota Repair Manual Volume 1 (Diagnostics) describes this as "Fuel injection time for cylinder No. 1" and goes on to say that when idling it should be in the range 1.0 - 3.0 ms. I would describe it as the time for which the fuel injectors are open each time they fire. It is interesting that the value tends to settle to around 7 ms above a certain power, additional fuel being drawn only by an increase in engine spin rate, not injector opening time.
The Toyota Repair Manual Volume 1 (Diagnostics) describes these items as "Abnormal revolution variation for each cylinder". It should normally be 0%, which is certainly the case for me. A careful reading of the manual suggests that a non-zero value for these items would indicate that the cylinder is not contributing its fair share of drive power due, for example, to persistent mis-fire, abnormality in ignition or incorrect injection of fuel.
This may be the time for which the DC-to-DC converter has been turned off to reduce the drain on the high-voltage battery during periods of heavy use. Or, it could be the number of times this has happened. For me, it always reads zero. If anyone sees anything else, especially if it changes with some identifiable condition, please let me know.
This item is described in the repair manual Volume 1 as "Cumulative number of times of battery dies". For me, it always reads zero. It has been reported to increase to 1 after running the car out of fuel and continuing driving to a very low battery SoC. No apparent harm came to the car as a result of this. In particular, the car started right up after refueling. So "dies" in the Toyota description can probably be interpreted as "falls to a lower SoC than is permitted in normal operation". This "battery dies" threshold could be anywhere in the range less than 33% to greater than or equal to 23% according to experimental results from multiple sources.
This may be the time for which the battery has risen above the maximum state of charge, which is thought to be 80%. Or, it could be the number of times this has happened. For me, it always reads zero. If anyone sees anything else, especially if it changes with some identifiable condition, please let me know.
This seems to be stuck at 20%. If anyone sees anything else, especially if it changes with some identifiable condition, please let me know. Note - this item sounds as if it's computed by the Mini-Scanner from other data, but it is not. It comes directly from the ECU.
Presumably the time, in hours, for which the ignition is off. However, this is not the time it was off before you last turned it back on. In my car, the value was stuck at 11 for a while and then changed to 12. I think it is some kind of averaged value but further investigation would be useful. It is set to zero by clearing DTCs in the Battery ECU.
The number of Diagnostic Trouble Codes stored in the Battery ECU. For me, this was at first stuck at 22, but had increased the last time I looked. It is set to zero by clearing DTCs in the Battery ECU. Further investigation is required.
The air temperature inside the main battery housing, or something like that. Maybe the exhaust air temperature, that is the temperature of the air blown out by the fans. Anyway, this and the following four data items are going to give you an indication of how hot the battery is and perhaps explain a "Mister Turtle" lamp on the dash.
The temperature registered by battery temperature sensor number 1.
The temperature registered by battery temperature sensor number 2.
The temperature registered by battery temperature sensor number 3.
The temperature registered by battery temperature sensor number 4.
The lowest voltage of all battery "blocks", in volts. A battery "block" is a pair of modules that are monitored as a unit by the battery ECU. Each module consists of six cells, so with twelve cells in total, a block has a nominal voltage of 12 * 1.2 = 14.4 volts. In spite of this, you are much more likely to see 15 to 16 volts when the battery is at rest (no charge or discharge current).
The reference number of the battery block that has the lowest voltage. In a healthy battery, this number is likely to move around between blocks having the same voltage.
The highest voltage of all battery "blocks", in volts. In a healthy battery, the difference between the highest and lowest block voltages will be around 0.1 volts.
The reference number of the battery block that has the highest voltage. In a healthy battery, this number is likely to move around between blocks having the same voltage.
Auxiliary (12 V) battery voltage. With the car on but not started, this will be around 12 volts, but with it "Ready" it will be close to 13.8 volts as a result of the DC-to-DC converter supplying power from the main battery.
Output, in millivolts, of oxygen sensor "Bank 1, Sensor 1".
Fuel trim due to the output of oxygen sensor "Bank 1, Sensor 1".
Output, in millivolts, of oxygen sensor "Bank 1, Sensor 2".
Last edited December 4, 2003. All material Copyright © 2003 Graham Davies. No liability accepted.