Toyota Prius Gen2 Board

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Prius Gen 2 Inverter Montage
Internal look at the Prius Gen2 Inverter
Prius Gen 2 Layout.jpg

The Toyota Prius is a hybrid vehicle. Their inverters are suitable and attractive for DIY EVs because of:

  • Large part availability, Prii have been made in large numbers for 20 years and spares are inexpensive.
  • High affordability. Prius inverters are available for around $150 from scrapyards everywhere.
  • Durability. Toyota engineers appear to have made the inverters foolproof, many inputs and outputs gracefully handle fault conditions.
  • Respectable performance. Rated for 50kW output, but tested to handle 600v, and 350+A for MG2 inverter, 250+A for MG1 inverter, 360kW total (480hp)
  • Ease of re-purposing. Emulating the original ECU seems reasonably feasible.

The Gen2 Prius (2004-2009 model years) has a variety of useful components inside the inverter package:

  • 2 high power inverters, for the 2 motors MG1 (starter) capable of handling 250 amps, and MG2 (drive motor) capable of handling 350 amps.
  • A DC-DC converter to provide 12v and up to 100amps power supply to the automotive systems and accessories.
  • A tertiary power inverter to run the A/C, CAN controlled via the "BEAN" (????) network
  • A boost module to boost the 200v battery pack up to 500v, which looks to be able to function as a battery charger (wish list for future development)
  • See this video for a thorough disassembly and explanation of the Gen2 Inverter (Timestamp 1:15:30):

32-pin Prius Inverter Pin mapping

32-pin Prius Inverter Pin Numbering
32-pin Prius Inverter Pin Numbering
32-pin Prius Inverter Pin Numbering
Pin # Designation Description Wire Color

(Inverter Side)

(See pictures to the right)

Wire Color

(Harness Side)

1 vacant
2 GIVA MG1 Phase Current V LightGreen White
3 GIVB MG1 Phase Current V Purple-Red Black
4 GUU MG1 PWM U - Speed Signal Wave Blue Black
5 GVU MG1 PWM V - Speed Signal Wave Blue-Red Green
6 GWU MG1 PWM W - Speed Signal Wave Yellow Yellow
7 MIVA MG2 Phase Current V LIghtGreen-Black Green
8 MIVB MG2 Phase Current V Purple-Yellow White
9 MUU MG2 PWM U - Speed Signal Wave Blue-Black Black
10 MVU MG2 PWM V - Speed SIgnal Wave Blue-Yellow White
11 MWU MG2 PWM W - Speed Signal Wave Yellow-Black Red
12 VH Inverter Capacitor Voltage Purple Yellow
13 CPWM Boost converter PWM switch signal Blue Black
14 CT Boost converter temperature sensor Green-Red Red
15 VL Boost converter input voltage Purple-White Yellow
16 GINV Inverter Ground Black-White Yellow
17 vacant
18 GIWA MG1 Phase Current W Grey Red
19 GIWB MG1 Phase Current W Grey-Black Green
20 GSDN MG1 Shutdown Brown-Black Red
21 GIVT MG1 Inverter Temperature Green-Black White
22 GFIV MG1 Inverter Fail White-Grey Grey
23 MIWA MG2 Phase Current W Grey-Green Red
24 MIWB MG2 Phase Current W Grey-Red Black
25 MSDN MG2 Shutdown Brown Green
26 MIVT MG2 Inverter Temperature Green Light Blue
27 MFIV MG2 Inverter Fail White Green
28 OVH Overvoltage Pink Brown
29 CSDN Boost converter shutdown signal Brown-White White
30 FCV Boost converter fail signal White-REd White
31 OVL Boost converter over voltage signal Pink-Blue Black
32 GCNV Boost converter ground Black-Red Green

DC-DC Converter

Prius Gen2 DC-DC connections.
DC-DC converter "C 5" connector

The onboard DC-DC Converter is powered by the high voltage traction battery to supply 12v and up to 100A for low-voltage automotive components and 12 battery maintenance, equivalent to an alternator or generator. Direct control of the converter is simple, only one 12v wire connected to Pin#1 of connector "C5" is necessary to activate it, but a second input can be added at Pin#4, to enhance control.

The 6-pin "C5" connector terminal positions and harness-side colors:

Pin # Designation Description Wire Color
1 IGCT 12v+ Blue
2 ID1 Not Needed Purple
3 S B+ (opt) White
4 NODD 0-5v+ Ppl/Gld
5 VLO Not Needed Blue
6 Vacant

The case of the inverter must be vehicle ground (12v battery negative terminal), just as an alternator or generator would be.

With the HV bus energized and switched 12v applied to Pin#1 of "C5", the DC-DC will produce 13.2-15.2 Vdc on the large C6 single-conductor connector nearby, which is equivalent to a 12v alternator/generator positive terminal. Depending on voltage applied to pin 4 (if used), output can be tailored; when grounded, it will act as a "KILL" input and DC-DC output will drop to zero. No base load is required to produce voltage.

Note: The output at C6 (large grey connector) is not internally fused and not disabled unless power to Pin#1 of C5 is off, or Pin#4 is grounded, but the DC-DC converter can only produce output when the HV bus is energized.

Note on Limitations - The DC-DC system is not designed to charge up a low 12v battery and certainly not one that's completely dead, doing so can damage the inverter/converter. Pin#1 can be tied directly to the same ignition switch signal as the control board receives as this circuit draws only about 6.3mA.

Inverter Cooling

The inverter is liquid cooled, coolant enters at the front and exits the rear of the inverter housing from the o-ring port connected to the Hybrid Synergy Drive (HSD) cooling system reservoir. Some type of circulating pump and radiator are needed to use Toyota inverters, many compact options are available.


Details on connectors and terminals have been posted on the IH8MUD website:

Alternatively, the Toyota wire repair book can be found here:

Please use either or both of the above to identify the connector and terminal numbers needed for your project.

Connector Male Female
C5 90980-10987 90980-10987
B+ (DC-DC output) 90980-11963
32-pin connector TE 1318747-1 (& 1123343-1 for pins)
28-pin connector (on inverter logic board) TE 1565380-1 (& 1123343-1 for pins)

Through Hole Control Board

Prius Board v1

The Toyota Prius Gen2 Board is an open source project to repurpose 2004-2009 Toyota Prius inverters for DIY EV use. It consists of a circuit board and programming that replaces the original logic board, connected to the inverter and allows independent control of it without communicating with a Prius ECU.

Note that there is also a Toyota Prius Gen3 Board for the 2010-2015 model years.

As designed by Damien Maguire, the open source hardware for the control board can be purchased as blank, unpopulated boards on his website: Prius Gen2 Logic Board on EVBMW's Webshop

How To Use

The Prius Gen2 Board is suitable to control any (please add: motor types here) motors.

Note: There is a mistake in the printing on the v1 circuit board. The parts labelled T1, T2, and T3 - which are the small black transistors in the upper right of the board - are all drawn backwards to how they need to be inserted. These parts should be installed with the flat side of the component facing the opposite direction as the printing shows. The flat side should be to the right.

Schematics, Bill of Materials, and other documentation are available on Damien's Project Github (note: flesh out bill of materials here, or post changes to Damien to update his documentation directly?)

Prius gen 2 inverter lower casing internals

The control board utilizes the Blue Pill (link?) micro controller, and takes advantage of the software (link?) for control. It is also connected from the outside via the main (32 pin white) OEM connector - try to retrieve this connector and part of wiring loom when sourcing your inverter. Picture of connector further down in wiki.

The control board design incorporates the use of the existing inverter Current Sensors - if FOC option is to be used (Gen 2 Transaxle MG2), bandwidth should be a multiple of control loop frequency which is 8.8kHz. (link to how to modify original setup?)

Functionality of the existing resolver is integrated as well.

Assembly notes? Blue Pill programming notes or just links to Blue Pill section?

Try to get all the wiring harness bits that plug into the inverter when you purchase it. Else, the 32-pin connector inside the inverter part number is: 1318747-1, and the pins to wire it are: 1123343-1

Terminal Block Connection list (rough, in-progress):

Wire Connections

Prius Control Board - Wiring Map (click to see fullsize details)

Control Board Pin mapping:

Pin # Designation Description
TB1-1 12v-in Primary 12v supply from ignition on
TB1-2 GND Primary ground connection to 12v negative. All grounds are common
TB1-3 5v VCC 5V supply from board for use with throttle pot or hall pedal
TB1-4 Throttle In 0-5v variable voltage input from throttle pedal or pot
TB1-5 Regen In 0-5v variable voltage input. Can be used as second throttle channel or control regen from a brake pressure sensor
TB1-7 Brake In 12v digital input from brake light switch.
TB1-8 Start In 12v digital input from "Start" position on a traditional ignition switch. Momentary action push button can be used.
TB1-9 For In 12v digital input commands motor to run in forward direction
TB1-10 Rev In 12v digital input commands motor to run in reverse direction
TB3-1 +12v VCC 12v output to inverter IGCT terminal (Not on the 32-pin connector, the red wire on the 2-pin connector next to it).
TB3-2 GND Common ground, but used to connect to inverter GND terminal (Not on the 32-pin connector, the black wire on 2-pin connector next to it).
TB3-3 Phase U

Phase U output. Connect to Inverter MUU terminal for MG2 inverter drive or GUU for MG1 inverter drive

TB3-4 Phase Y Phase V output. Connect to Inverter MVU terminal for MG2 inverter drive or GVU for MG1 inverter drive
TB3-5 Phase W Phase W output. Connect to Inverter MWU terminal for MG2 inverter drive or GWU for MG1 inverter drive
TB3-6 Current U Phase currents from inverter. Requires external divider circuit. Not required to run motor or inverter.
TB3-7 Current Y Phase currents from inverter. Requires external divider circuit. Not required to run motor or inverter.
TB3-8 MG2 Enable Connect to Inverter MSDN to run MG2 inverter or GSDN to run MG1 inverter
TB3-9 MG2 Fault Connect to MFIV for MG2 or GFIV for MG1
TB3-10 DC Bus Connect to inverter VH to measure DC link voltage
TB2-1 +5V VCC 5v output to encoder for induction motor
TB2-2 ENCA In Encoder input A
TB2-3 ENCB In Encoder input B
TB2-4 GND Encoder ground
TB2-5 HS Temp Heatsink temp sensor input
TB2-6 MOT Temp Motor temp sensor input
TB4-1 GND Common ground
TB4-2 Main Con Main HV contactor control low side switch
TB4-3 Precharge HV precharge contactor control low side switch
TB4-4 +12 V VCC Spare 12v output
TB4-5 CAN L Can bus low signal
TB4-6 CAN H Can bus high signal

New SMD control board with enclosure and designated pinouts

Please add pictures and description.

Pin Mapping - Note : Smaller 12-pin socket is the interface to the inverter & 20-pin to the motor

32 Pin Main white connector Gen 2 Inverter emplacement

20 - Pin socket

Pin#01 - ENC_B/S3

Pin#02 - S1S4

Pin#03 - ENC_A/S2

Pin#04 - R1

Pin#05 - R2

Pin#06 - 5V

Pin#07 - THROTTLE 1

Pin#08 - THROTTLE 2

VCU to Prius Gen2 wiring v1.1

Pin#09 - START_IN (12V)

Pin#10 - BRAKE_IN (12V)

Adapter Board Pin out locations

Pin#11 - FORWARD_IN (12V) (1, 2 or 3 way switch)

Pin#12 - REVERSE_IN (12V) (1, 2 or 3 way switch)

Pin#13 - Motor Temp -

Pin#14 - Motor Temp +

Pin#15 - DC (HV) Switch Control (Ground signal)

Pin#16 - Pre-ChARGE Control (Ground signal)

Pin#17 - CAN L

Pin#18 - CAN H

Pin#19 - Ground

Pin#20 - 12V "Ignition"

12 - Pin socket ( starts at pin number #21) - Corresponding pin on Main White 32 pin Inverter connector is in brackets.

Pin#21 - GIVA (2)

Pin#22 - MIVA (7)

Pin#23 - GIWA (18)

Pin#24 - MIWA (23)

Pin#25 - VH (12)

Pin#26 - MIVT (26)

Pin#27 - MFIV (27)

Pin#28 - MUU (9)

Pin#29 - MVU (10)

Pin#30 - MWU (11)

Pin#31 - CPWM (13)

Pin#32 - GINV/GCNV (16/32)

Connect MSDN Pin#25 in inverter (not 25 on controller) permanently to 12V to enable the MG2 Inverter (can be tied to same 12v source as "I9")

Connect CPWM to 12V via a 470 Ohm resistor for charge mode.

Connect the 2-pole white power connector ("I9") inside inverter to 12V and Ground to power up inverter electronics.

Make sure to connect Pin #32 and GINV/GCNV to vehicle ground.

Initial Set up

Step 1 : Solder relevant (and included) connector pins to the Adapter Board

Step 2 : Plug in Wifi Adapter and connect ONLY Pin#19 - GROUND and Pin#20 - 12 Volts power supply

Confirm PWR LED lights up along with WIFI LED. Confirm ALIVE LED flashes.

Step 3 : Connect computer/laptop to the wifi network (Example - Inverter 7)

Step 4 : Go to browser toolbar and type in + Enter. (allow pop ups/Trusted site). Confirm Web based Interface appears and list of parameters appear.

If parameters appear, you are now connected to the Adapter board and the Web based Interface - Congratulations - You are now in the Matrix !

Step 5 : Wire up 12 Pin SMD board connector to corresponding 32 Pin Inverter connector, permanent 12 volt supply to Pin #25 (MSDN) of Inverter, and 12V and Ground to 2-pole Inverter connector (next to main 32 pin white connector)

Step 6 : Connect fused 12 volt and Ground to HV Inputs (battery), along with 55 watt light bulb in series (resistor) on the Positive line

Step 7 : Connect fused 12 volt power supply for SMD board , Pin #25, and Inverter 2-pole connector - You are now set up for basic Open Loop motor spinning!

Step 8 : Connect 21 watt light bulbs in Delta connection to the 3 PWM outputs in Inverter (no motor) -

Step 9 : Web Interface Basic parameters set up - to confirm PWM outputs : Full boost with 12v supply, default forward, ampnom @ 70%, and fslipspnt @1 Hz. Select - "Start Inverter in Manual Mode" Confirm flashing lights.

Step 10 : Connect motor phase wires to inverter PWM outputs. Repeat Step 9 and change "fslipspnt" by 1 unit at a time, until motor spins smoothly. (I noticed Light bulb resistor on HV line lights up when no spinning) along with high current values. Once you have the motor spinning, continue to increase the "fslipspnt" value whilst monitoring the current (ampmeter on PWM output wire) You will also notice the light bulb starting to fade untill there is no more light. Optimal motor spinning in Open Loop Mode ! (these values are related to a 12 volt HV supply - re using these parameters is still to be verified at greater supply voltages)


The Control Board runs Open Inverter software. A set of known-good default inverter parameters can be found here:

Do NOT program a deadtime value for the Gen2 inverter. It only uses 1 PWM per phase and the inverter itself generates a low-side and high-side signal WITH deadtime.


The gen 2 can only charge in buck mode. So maximum charge voltage is limited to the rectified AC input. E.G. From a 230 VAC source the inverter can only charge up to around 320VDC

Relevant Parameters

Charge mode:Buck

Chargecur: 1.5

Chargekp 20

Chargeki: 10

Chargeflt 2 dig

Charge pwmmin: 10 (Change this to get equivalent to min battery voltage.)

udcswbuck: x (HV bus voltage at which point Ground signal is used to control AC and HV battery relays)

Relevant Pins

  • CSDN (pin 29 on inverter)
    • Shuts down high and low IGBTs when fed 12v, via 470R
    • When CSDN is HIGH both IGBTs are OFF.
  • CPWM(pin 31 on control board, 13 on inverter)
    • Enables charge mode when fed 12v via 470R
    • When CPWM is HIGH, the LOW side IGBT is on(shorts out battery), when CPWM is LOW the HIGH side IGBT is on.
  • Forward and reverse (11 and 12 on control board)
    • Both must be high to enable charging
  • DCSW switch(15 in control board)
    • Controls DC relay switch.

Physical setup

  • 240v AC plugs into two MG1 phases, with a precharge resistor always on.
    • Relay controlled by DCSW pin connected to ground side of relay signal wires.
  • HV Battery connected with precharge resistor
    • Relay controlled from DCSW pin connect to ground side of relay wires.
  • CPWM to 12v via 470R resistor. Pulled high to when you want to charge
  • CSDN pin to 12v via 470R resistor. Pulled high to when you want to charge
    • CSDN pin also tied to DCSW signal pin, which pulls it down when precharge is complete.


  1. Fwd and reverse signals high, relays open
  2. CPWM and CSDN pulled high via 470R .
  3. Connect AC input voltage with precharge
    1. DCSW will then close relays and pull down CSDN pin to activate charging.
  4. Activate buck on charger. (By manual web interface or does just having FWD and Reverse high activate this?
  5. To stop, can change chargecur to 0 or switch off inverter power.