All about the Toyota Prius

Part 1 -- Introduction

Images are linked to larger versions.


Who is "Hobbit"?
    I'm that loose nut behind the wheel

Background: all tech, all the time
    Computers/network security
    Theatre lighting/production tech
    Minor vehicle-hacking over the years...

The Prius brought my vehicle interest out of hiatus
    Originally wanted hybrid minivan, settled on this
    Absolutely no regrets, absent the 100 MPG box-truck


Spreading the word

Grassroots evangelism at car/energy shows
    The numbers game -- everyone wants the MPG hints!

There are many internet owner communities
    Priuschat, priusonline, yahoogroups, ...
    Strong tech/engineering forums, too

Google for "hobbit" and "prius"
    My own Prius hacks/discoveries detailed up there
    Pointers to numerous other resources



Toyota doesn't provide these
    So I did, and it really helps
    We will explore all this in more depth

EWD and parts-location became my bible
    Very minimal harness mods
    No operational mods (yet...)

Driving barefoot helps, too!



    Whichever way you go at it...

The results speak for themselves


Shadetree mods

"This is a NEW car, right?"
    -- great quote from a friend



Different ways of thinking

It's a normal car
    Just put it in "D" and drive!
    Toyota did a nice job on ease of use

It's a very strange car
    Electric CVT
    Idle-stop, even while moving
       (Think "steam engine"?)
    Stealth mode, electric-only propulsion
    Some unusual controls

An elegant blend of many technologies
    whose quirks we will learn about in detail


New building blocks

Familiar parts
    Engine, ECM
    Brake ECU (ABS)
    12V battery, now called "aux"

New parts, green parts
    Hybrid controllers
    Traction batteries
    Inverters, DC/DC converters
    3-phase electric motors
    Drive-by-wire (partial)
    Regenerative braking/integration
    New electric subsystems
    New cooling systems


Prius terminology

NHW10 -- Japan only
    This is really the first generation
    We can conveniently ignore it for now

NHW11 -- "Classic" sedan
    First US release, 2001 - 03
    We will call this "1st gen"

NHW20 -- '04 and up hatchback
    technically, it's the 3rd generation
    We will call this "2nd gen"

There are MANY more 2nd-gens out now
    May 2007: a RECORD Prius sales month
    '01 - '04 starting to fall off warranty



Smart-key fob contains metal key for driver's door
    That's the only physical lock on the entire car

1st-gen has traditional key

2nd-gen has the "smart fob"
    And "smartkey" isn't just in the Prius now!
    It knows where you are around/in the car
    Walking away with key does NOT cause shutdown!

Fob slot is just a transponder reader
    Similar to company door-access RFID card
    Dead fob battery? Not a problem, passive chip
    No slot in Camry hybrid, just a magic area on the dash

Myth: New fob needs new ECU
    There's a re-authorization method via Toyota


Smart key disable

For less confusion in the shop, turn it OFF

All described in the owner's manual!


1-2-3 Instructions

Valet cards that come with the car
    But there's a lot more to it...


Power states (2nd gen)

    Like traditional key, but uses button pushes (without brake)

Foot on brake is a shortcut to READY
    Unless you're already *at* READY, then it turns off

KOER no longer means "Running"
    Key on, engine Ready? But the power LED is *OUT*!
    It can start up any time, like a home furnace...
    ... right in the middle of an oil change?!

Knowing these states is critical
    And when/how to best use them
    Some test scenarios depend on power transitions!


Shift states (2nd gen)

Each "position" is momentary
    All electronic -- it could have been pushbuttons

Separate Park button to avoid mistakes
    (although the computer sanity-checks that)
    Auto-Parks on power-down

Foot on brake permits leaving Park
    Brake light switch therefore MUST work

"Transmission creep" is electric
    See NHTSA site for safety rationale

Reverse is electric-only

Neutral is special (yellow highlight)
    Half-second hold delay -- a little funky to get used to



In Park: start/rev-up on pedal push
    Cranks the ICE at 1000 RPM
    Races up to 2400 or so
    NOT useful for compression check -- too fast

Neutral: no change permitted
    Cannot stop/start
    Maintains base engine idle
    Fancy footwork to make it run: Brake + Go + N
    Sometimes needed for inspections [the Georgia problem]

Beware: cranking sounds like running



It's the whole point of these cars
    The customers care, we should too

Independent throttle control
    Takes that away from the user
    Tracks optimal BSFC map -- mostly...

Pulse and Glide technique
    High on the efficiency curve, or OFF
    RPM maps nicely to power output
    ... so why is there no TACH?

Kilowatts vs. horsepower
    A hundred willing slaves on a rope?


Demo time!

Learn the dash / controls
    And what the MFD (Multi-function display) shows

See what I've added

Learn the states and tricks
    Find Neutral reliably
    Find the one wrong arrow


Safety first!

Lethal voltages and current capacity
    It's all about current through the body
    If 60V can kill, what can 300V do?

Semi-standard cable colors
    Low: < 30V, red/black 12V type
    Intermediate: < 60V, blue or green
    High: > 60V, orange


Safety first!

Remove jewelry, watches, phones, etc
    Metal objects increase contact surface area
    Metal objects conduct high current and BURN

Wear 1000V gloves near ANY live connections
    Test gloves for pinholes/leaks

Cat III meters/scopes/leads
    Same gear used by electricians


Safety first!

Don't do this


Service plugs

Disables the HV battery pack

Orange color, obvious handle

Rear of car
    Driver's side of pack

Use gloves!
    Especially in any damage/unknown situation
    Removing glove outers may help dexterity

2nd-gen handle is a little special
    Pull straight up, then swing out and down 90 deg
    Reverse to re-insert
    Handle *must* do that final click-down!
       Part of a low-voltage interlock loop


Service plugs

Basic HV circuit
    Usually splits about halfway along

Sometimes contains the pack fuse
    1st-gen Prius: no
    2nd-gen: yes

A backup for welded contactors
    Ford uses a rotating plug
    Honda uses a switch w/ cover
    GM/Saturn -- varies

Wait 5 minutes for discharge!
    How do you check??
    Sometimes you can't until covers are removed


Fuse inside 2nd-gen service plug

(This one went swimming)


Service Safety

Lift points
    Look it up, don't guess

Avoid HV cables underneath!

Is it really shut down? Make sure
    Disable Smartkey (SKS) as you receive the car
       ("KEY" button under column should be IN)

Vent all exhaust
    It's clean, but not that clean

Standby systems
    Brake pressure self-check
    Door switches can activate many things
    Coolant storage self-check, 5 hours later


Emergency response

OEM sites all have ERGs up for free
    Honda: turn off, remove key
    Toyota: power down, check for no READY
    Ford: power off, discon. 12V, pull service plug
    GM/Saturn: pop "disconnect control" switch

Only a couple mention service plugs

Certain fuses/relays are detailed
    (IGCT, HEV, etc)

All say: kill the 12V system

Lessons from EV competition rules?
    Outside accessible, labeled HV disconnects


Emergency response

When in doubt, look it up

Useful related sites:
    Wrote many of the OEM manuals, esp. Toyota
    Nice technical overviews of many hybrids

Safe cut zones usually shown
    Avoids airbags, HV cables, etc

Safe vehicle stabilization
    Cribbing points away from HV wiring


Myths and answers

First-responders should be confident

You will NOT be electrocuted by:
    touching a crashed hybrid
    touching a flooded/submerged hybrid
    dousing a burning battery pack

    HV systems are isolated
    Batteries and relays are in a steel box

Just don't cut any HV wires!
    Be careful where/how you lift, too

Airbags/SRS and fuel are more dangerous


NiMH Electrolyte

Potassium hydroxide == potash == soap?
    Flush with plenty of water
    Vinegar or boric acid can help

NOT really a HAZMAT situation
    it's hard to actually get on your hands!


Other battery safety

Painting booths
    Remove HV pack and 12V before baking
       (a revenue opportunity from body shops?)
    Temp above 140F is bad for any battery

Stereo/accessory mounting?!
    Screw through HV pack == car doesn't work
    Instant ground fault!
    (Yes, it has happened, and nobody died)


Demo time!

Shake hands with electricity


Service plugs



Service environment

It's fairly routine, really
    40% maintenance
    40% generic repair
    20% diagnostics

Know the car!
    Customer confidence will help bring them in
    Yes, these are picky/knowledgeable owners
    Take note of their MPG averages...

Dealership horror stories are common
    Here's our chance...


Service environment

Maint schedule is fairly sparse
    5K: change oil/filter, maybe rotate tires
    10K on synthetic?
    Brake pads? Hah!

Wrong oil can cause no-starts
    This is becoming critical in ALL cars

Use the right fluids, OE where possible
    DOT 3 brake fluid (not 4)

Two coolant systems plus one A/T
    1st-gen transaxle: type T-IV
    2nd-gen transaxle: type ATF-WS
       (WS is a good upgrade for Classics!)
    Toyota super-long-life coolant, no aftermarket yet

Both fluids are pink!
    Don't second-guess the chemistries -- look it up!
    Motor insulation breakdown is a bad thing


Service checks

    Make sure 12V/14V is healthy
    There's no alternator
    IG-ON vs READY for many tests
    Inspection mode (don't really need it)
    Can't snap throttle from underhood!
       (Can't cheat and pull motor wire, either)

    CAN bus is unbuffered at DLC 6 and 14
    Terminated at ECM and HV-Batt (120 ohm)
    Without it you go nowhere; be careful what you plug in

Official scantool
    Mastertech 3100 with recent Toyota OE cartridge
    Aftermarket isn't quite there yet...
    Body ECU: OEM tool only?
    Customers may ask for "settable options" changes


EU scantool

Newer and slicker than Mastertech ...
    But still has a few issues

New US OEM is called "Techstream"
    Ruggedized laptop-based, Wifi straight to Techinfo
    Just starting the rollout, only a few deployed


Oil change light reset

Resetting the "MAINT REQD" light that appears every 5000 miles
    First, turn car OFF and change the oil if needed
    Avoid overfills. See the "engine" section later on for why

    With power on, tap the ODO/TRIP button to get to
       the odometer display (not trip A or B)

Then, power the car off...


Oil change light reset

While holding the ODO/TRIP button DOWN, power on again
    (IG-ON is sufficient)
    Keep holding the button

You should then see the "reset dance"
    Wait until it finishes and returns to the odometer
    reading, then let the button up. Done.

Many newer cars have similar procedures!



ECU and relay access
    Panels pull straight off, don't break tabs
    Sheet metal burrs inside -- ouch!

Major ECUs under pass. end of dash
    Fairly easy to backprobe, but watch pin size

CND situations
    Four reboots clears MIL (IG-ON usually counts, but not always)
    History codes slowly disappear (# trips)
    DOME fuse is ECM keepalive, misc standby
    Some nonvolatile memory (notably skid-control)

Re-learn after 12V loss
    Power window auto-up
    Radio, clock, beeps, MPG average (!)
    Fuel map trims??


Parking games

How to leave the car in Neutral

1st-gen has traditional lever/linkage
    Oddly placed, but still PRNDB
    Emergency park release under column

2nd-gen is more difficult
    Electric pawl actuator, special 3-phase drive motor
    Shift to N, then pull the PCON MTR relay
    That disables Park, but the car gets unhappy
    Do what the screen says: set emergency brake
    ... then you can at least shut down

Once restored, clear the error state DTCs



'06 and up have valvestem TPMS
    Be careful when busting, as usual
    Sensor range is ~ 60 ft
    Inter-car interference is possible!

Inflation pressure?
    Many owners run 'em hard (ahem)
    3 - 4 psi F/R diff to match for load

HAND TORQUE please -- no impact


Demo time!

Find the ECUs

Classic park-lock bypass [?]

2nd-gen park bypass and recover

Onto lift and have a look under

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