All about the Toyota Prius

Part 3 -- Operation

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What happens when we power up

(Caveat: mostly describes 2nd-gen...)

Immobilizer conversation
    Fob-slot switch and/or SKS sensing

    Clock, stereo, MFD, power-outlet

    All ECUs boot up
    HV battery ECU enabled (can read SOC, block voltages)
    But HV battery itself is NOT online yet
    Normal systems (windows, wipers, etc)
    Neutral enabled (2nd-gen)


Network chatter

Three main networks in 2nd-gen
    CAN -- high speed, 500 kbit/s
    BEAN -- body electronics
    AVCLAN -- stereo, nav, phone, etc
    Screen beeps are AVCLAN command to stereo

Major players for driving:
    Hybrid ECU, engine ECM, skid-control, battery ECU
    Steering-angle and yaw if VSC option

Gas gauge all-blinking means "no network"
    Which means your scantool won't work either


READY mode

Can shortcut to here w/ brake switch
    But everything else listed previously happens anyway

Inverter precharge (20 ohms)
    Prevents huge current spikes
    Main (+) connects after short delay

Battery contactors
    Listen to click pattern back there

DC/DC converter starts
    See jump to 13.8 - 14 V

Coolant storage pump-in
    See ECT tick up and then slowly fall
    Doesn't always happen...


READY mode continued

Engine starts ~ 12 sec into it
    unless we quickly select Neutral or EV-mode
    1000 RPM cranking *sounds* like running!
    "Runs, then dies" complaint may be a plain ol' no-start

Retarded warmup run, ~ 1 minute
    You can *hear* this underneath
    "Flames roaring down into the cats"
    Some battery charging for extra load
    Higher fuel consumption!

Engine not used much at first
    Car moves on electric-only during that first minute
    You can drive away, but be gentle


READY mode continued

No shutdown until 40 degC ECT
    Unless you punch the EV button...

"Five stages" document tells whole story

1st-gen is a bit simpler:
    No coolant bottle, no EV, no CAN
    HCAC valve and VSV purge command after warmup

Both methods reduce cold-start emissions


Diagnostic hints

    Battery relays
    Inverter coolant pump
    ETCS motor PWM

Neutral prevents first engine run
    If your timing is right...
    Useful for "4 drive cycle" MIL self-clearing

Quiz: why does the car shake in Neutral idle?
    Hint: inertia
    (well, *I* thought it was misfire at first...)



Can we go yet?

Foot on brake!
    Review shifter state chart...
    2nd-gen beeps twice if you do something wrong


2nd-gen parking actuator

1st-gen: manual parking linkage

2nd-gen: electric parking actuator
    (shown here)
    Again, something you can hear
    60:1 harmonic drive, to forcibly pull pawl
    Remarkably fast given the gearing ratio...

3-phase brushless motor, driven from ECU
    Passive reluctance rotor, not permanent-magnet
    Hall sensors feed back to ECU to confirm operation
    (This is how the car knows when it's disabled)


One small step...

Accelerator by-wire

1st-gen: dual-wiper pot
    Reliability issues -- "big hand" syndrome

2nd-gen: dual Hall-effect
    Much more noise-immune and smooth

Driver demand
    Humbly beseech the hybrid ECU to go faster
    Engine run/stop based on MANY factors
    Battery usually seeks 60% SOC

    Brake + Drive + accel
    Like tranny-loading, but only up to a point


Math is hard

Hybrid ECU does a lot of this
    Read inputs, do math, control the motors
    Ask for engine torque (or not)
    HV ECU gets NEO copy of CKP for RPM and TDC

Exact algorithms still unknown
    ... after five years of guesswork!

A few parameters and thresholds
    Temps, speed, demand, SoC, RPM, braking, ...
    And *rates* of change, which is very cool

At 60% SoC, ICE-on threshold == 10 kW
    Mostly NOT based on vehicle speed...
    Response hysteresis


Engine/CVT management

High ICE torque load most of the time
    Nonlinear throttle response
    Basically "snaps" open near bottom
    From there, it's all about RPM
    This sits well with the hypermilers...

Variable "ratio" is very wide
    To "upshift", back off your foot!

Fake coasting drag is really mild regen

Quiz: What's MG1 RPM here?
    I'm doing 66 mph turning 1800, so ...


Our old friend

Heretical mode
    The red line is a hint..
    MG1 must be pushed backwards
    Negative split, overdrive, etc

Miscellaneous limits and states
    6500 or 10000 RPM on MG1?
    up to 41 MPH electric-only -- protects MG1
    Full operation above 70 deg C engine temp
    No-ICE "B" below 20 MPH
    Warp Stealth > 42 MPH
    Warp Neutral ...

The list and the fun goes on...
    As does the confusing terminology

But the OWNERS know all about it!


Demo time!

Observe start, warmup and drive cycles
    And all the operational hints

Graph MG1 RPM

Compare scantool vs. gauges

Force charging



Brake by wire

Brake by wire, with backup systems
    This is one of most complex aspects of the car

Skid-control ECU, actuator drivers
    Spikes are heatsinking
    ECB is ABS on steroids -- pump, valves, ECU, etc
    But with MUCH more integration w/ hybrid system
    ... so what's this "regen" thing?

Other things visible here:
    DLC3 above driver's right shin
    Small grey box is a warning beeper


What's a braking request?

Braking request == CAN traffic
    Skid-ECU: "I want this much negative torque"
    HV-ECU: "I can give you this much"
    Foot pressure is simply stored and returned

MG2 commutated as a generator
    Energy sent straight into battery
    Regen limit == 50A in Classic
    100 - 120 A in 2nd-gen (pack fused at 120!)

Skid-control ECU handles the excess
    Hydraulic pressure metered out to wheels
       (rears first, for balance)

Hydraulics used as LITTLE as possible!
    2nd-gen regen efficiency improved over Classic

GAME OVER at 7-8 mph
    Insufficient motor RPM anymore, even with boost
    Fall completely to hydraulics for remainder
    It's easy to feel that transition


Hydraulic system

Most of this is in the actuator block
    Solenoids, pump, pressure-sensors

Braking request == MCYL pressure
    Request read from PMC1 and PMC2 (red)
    Fluid redirected to stroke simulator spring-piston
       to provide normal "brake feel"
    SMC1 and SMC2 normally closed off

Wheel pressure sent from the accumulator
    Apply/release solenoids do their dance
    Pxx per-wheel sensors provide feedback

Stroke-sensor pot on pedal is for speed only
    Quick swing == panic stop, don't regen
    Medium swing == mix of both, not all-or-nothing

Bumps cause regen torque/current blips
    System gives up on regen at that point!
    ... until some indeterminate time later ...

Many newbie owners ask about pump noise


Backup systems

Power supply and capacitor bank
    Think of it as "vacuum boost reservoir"
    Enough for a stop or two if 12V goes
    It's in the BACK, next to the 12V

Direct hydraulic to front wheels
    If all else fails (or no power), SMC1 and SMC2 open
    No assist, but you can limp home
    ...or to the dealer...


What could go wrong?

For example, PMC2 stuck at 5V ...
    Highest input takes precedence?? Yes, apparently
    Only one of three inputs, no "voting"
    NASA would disapprove!

Skid ECU is powered even with car off
    First brake-light tap enables it
    Stroke pot monitors re-activation threshold
    You can hear high-pitch solenoid modulation

Careful study is well worth it


Brake service

Safety: pull accumulator relays
    Two ABS MTR in front block
    Slow press-n-hold cycles until beeper stops?
    Scantool "zero down" and "ECB prohibit"

Depressurize before disassembly!
    Reserve is high-pressure nitrogen cylinder
    Over 2000 psi on tap
    System self-recalibrates 2 minutes after shutdown

Brake/ABS blink codes via grounding TC
    DLC pin 13 -- y.a. custom assignment
    Look up the code-clear procedure...


Brake service

Bleeding procedure is VERY complex
    Easier with a bi-dir scantool
    Don't let ANY air enter the actuator/accumulator

Many calibration levels in memory
    Do not interrupt self-initialization!
    All detailed in repair manual
    "liner valve" means "linear"

Otherwise, they're ordinary brakes
    Pads/shoes last a LONG time!


Owner complaints: grabbing

Surfaces rust up due to less use!
    especially inner side Classic rotors, not sure why yet

Use Neutral trick to clean
    get to speed, select N, brake evenly to slow
    Ooh, energy loss!


Owner complaints: MPG

Am I regenerating?
    check ABS/brake lights & codes
    check HV battery current when slowing!

Overuse of electric-only
    Conversion inefficiency

B-mode myths
    No, it doesn't mean "battery"
    Like dropping into "Low"
    It's fairly complex, see my writeup..

Diagnostic thought process
    Customer: "I hear a suspension klunk when braking"
    Tech: "During regen or physical?"


Demo time!

Mess with regen, watch IB and pressure

Pull ABS MTR and drive/watch

Invoke ECB PROHIBIT and watch



12V battery

Rear of car
    Left side in Classic
    Right side in 2nd-gen

AGM type, smallish capacity
    Heaviest load is probably the brake accumulator
    30A capability can jump the car

Use a "smart" charger

Features to note:
    The red cover is a PITA
    Main 12V fuse is under it
    Small white wire is voltage-sense direct to DC/DC
    Black box is brake power supply/caps
    [the blue Anderson connector here is NOT stock]

No aftermarket 12V for 2nd-gen yet
    Some owners have kludged in Miata units


12V currents

Startup current draw
    Accumulator pumping (brake pedal)
    Booting -- see "start" section
    Coolant pump probably *just* started...
    Drops negative as DC/DC comes online

Electronics base load is 300 - 400 W
    aka 2 amps from HV battery

"OFF" draws about 11 mA
    Smartkey enabled == considerably higher
    "Dead Prius" in airport lot...

Prius can !carefully! jump other cars
    100A limit, so just let target battery charge
    UNHOOK before target tries cranking



Electric steering assist
    ECU/driver and motor behind dash
    Worm angle allows manual turning

Evolution of torque sensors
    1st-gen: pot wipers
    2nd-gen: inductance bridge

Steering shaft recall
    Many Toyota models affected
    Driver + assist torque is powerful!

Common complaint: dim pad button light



3-phase scroll compressor
    With its own inverter section

Variable speed

Runs from HV battery
    Why? Think "2 KW" in terms of current

1st-gen is traditional belt-driven
    Engine runs whenever A/C is on
    This is why they're going electric...


Relays, wiring, etc

Drivers-side junction block
    Contains body ECU -- see "bodyecu" webpage:
    Four relays are *totally* buried in here!
    Likewise with some relays in underhood block

Major fuses are a single link-block
    Potentially expensive proposition

> 2000 pin/socket connections in the car!

Inverter pump runs all the time
    Surprisingly robust? Few if any replacements

2nd-gen has electric hatch latch
    There *is* a release, well-hidden


Demo time!

Current-ramp some ancillary devices

Run A/C from MG1

Find the hatch release


Real-life Problems

1st generation
    HC adsorber valve rust-up (P1430 etc)
    Original GS 12V battery (TSB EL014-03)
    HV battery terminal corrosion fix
    P3190, P3191 sporadic no-starts (TSB EG011-03)
    Throttle body crud
    "Big hand" syndrome, accel pedal
    Wheel bearings at 100K?
    Very early injectors?
    '01 Power steering rack and sensors
    Inner rotor rust
    ECU upgrades (8 yr warranty)


Real-life Problems

2nd generation
    Display-screen degradation (reman available)
    Brake light switch flakey (warr. repl)
    Engine compartment gasket
    Inverter coolant leak (EG017-05, rare)
    Stalling (SSC-50P), all over the news
    Steering shaft recall
    "Lifetime" transaxle fluid?? wrong
    Cowl drain holes (mine, anyway)
    ECU upgrades (8 yr warranty)



Advise the customer...
    Brakes grabbing (8 mph) -- use N trick
    HV Battery temp limits current -- known
    HV Battery maint. cycles (rare) -- known
    Blind spots -- move the mirrors
    Engine runs more for cabin heat -- bundle up
    Traction control "loses all power" -- be patient
    Tank bladder in the cold -- fill slowly
    Loose gas cap -- evap
    Out of gas! -- duh...
    Cell phone pairing?
    That Smart-key you disabled earlier...

Cars generally very reliable


It isn't perfect

Drain holes plug up easily
    Could flood into blower inlet

OEM tires
    Many complaints


It isn't perfect

Body flex
    But there's an elegant solution!

Repair costs
    Large expensive FRUs
    Totaled for minor damage?
    Forums encourage "get genuine Toyota parts"

    Substandard gauge (the NEC would disapprove)
    Tight harness sections
    Buried parts
    Really oddball color assignments...

Exhaust path
    Hangs a bit low past the fuel tank
    Not 100% stainless?


It isn't perfect

    Need working MFD to run heat, audio
    Need HV battery/system to start/run
    Meter module drives backup lights?!

Scantool info issues
    Standardization nightmare
    OBD Protocol bugs in '04 (SSC 40D)
    NO aftermarket has 100% OE level support yet
    This is not the IETF, mandates are needed

No more 12V --> HV boost charger
    The NHW10 early Japanese model had one!
    Ford kept the clue about that for the Escape



Sometimes Toyota just screws up
    Reversed starter-hole blockoff plate
    MG position-resolver harness at some risk
    Stony silence in response


Demo time!

Scope some signals, compare with Techinfo

Scantool comparison/shootout

Find the #1 injector line
    watch results of bi-dir injector cut

Diagnose some faults
    Both known and unknown...


The Future

Plug-in hybrids (PHEV) are coming
    Several prototype Prius efforts out there
    Learn motors/inverters/batteries NOW
    10 KWh handles avg. 40 mile commute
    Prius PHEV is ignoring the oil pump!
    What about city dwellers??

Current hybrids are a "bridge"
    Or a stopgap, depending on how you see it
    "Half a pack a day is still smoking"

Power-wagon hybrids aren't helping


Who killed the electric car?

The Rav4-EV pack
    > 100 mi range
    Toyota has killed this, too
       (with a little help from Cobasys)
    Didn't get nearly as much press..

New efforts, consumer pressure
    The treehuggers have the right idea?
    Now, if only the administration did...


Cleanup time!

Let's put all that stuff back together...

And thanks for being here!