4 SPEED AUTOMATIC APPLICATION PIGTAIL

🔧 LEXUS V8 ENGINES LLC

CLIENT PLUG CONNECTION GUIDE – 4 SPEED AUTOMATIC APPLICATION

(12-Pin Transmission / Shifter / Cluster Interface Plug)

📘 OVERVIEW

This document provides instructions for connecting the 12-pin client plug supplied with your standalone harness for 4 speed automatic transmission applications.

This connector provides the interface between the engine / ECU system and the vehicle for:

• Gear      position indication
• Overdrive      control
• Cruise      control operation
• Dashboard      / cluster integration

⚠️ IMPORTANT:
This is a standalone system interface connector.
All circuits in this connector are low-current signal circuits unless otherwise noted and must be connected correctly to the vehicle wiring system.

This base document covers the standard 4 speed automatic functions. Any additional pin assignments specific to the individual harness build can be added where applicable.

🔌 CLIENT PLUG DESCRIPTION

The 12-pin client plug is designed to provide the transmission-related signals required for correct operation of a 4 speed automatic system.

These include:

• 12V      gear position outputs
• Overdrive      control input
• Cruise      control inputs
• Cluster      / dash interface signals

All wires are labeled and correspond to the functions listed below.

🔑 PIN DESCRIPTIONS

Pin 1 – PARK (P)

12V Output – Park Indicator

This wire outputs +12V when the transmission is in Park.

Function:

• Used      to operate the Park indicator in the instrument cluster
• Can      also be used where a vehicle system requires a Park status signal

Operation:

• Transmission      in Park: wire outputs +12V
• Any      other gear selected: no output

Installation Notes:

• Intended      for indicator / signal use only
• This      is a low-current output
• Do      not use this wire to power high-current loads directly

Pin 2 – REVERSE (R)

12V Output – Reverse Signal

This wire outputs +12V when the transmission is in Reverse.

Function:

• Used      for reverse indication on the dash / cluster
• Can      also be used as a reverse signal for reverse light control

Operation:

• Transmission      in Reverse: wire outputs +12V
• Any      other gear selected: no output

Installation Notes:

• If      being used to operate reverse lamps, it is advisable to use this wire as a      relay trigger where required
• This      is a low-current signal output, not a high-current lamp feed unless the      receiving circuit load is known to be suitable

Pin 3 – NEUTRAL (N)

12V Output – Neutral Indicator

This wire outputs +12V when the transmission is in Neutral.

Function:

• Used      for Neutral indication on the cluster
• Can      be used where the vehicle requires a Neutral status input

Operation:

• Transmission      in Neutral: wire outputs +12V
• Any      other gear selected: no output

Installation Notes:

• Intended      as a signal output only
• Can      be connected to the vehicle’s Neutral indicator input where applicable

Pin 4 – DRIVE (D)

12V Output – Drive Indicator

This wire outputs +12V when the transmission is in Drive.

Function:

• Used      for Drive indication on the cluster
• Indicates      normal forward driving range

Operation:

• Transmission      in Drive: wire outputs +12V
• Any      other gear selected: no output

Installation Notes:

• This      is a low-current signal output for indication / interface purposes only

Pin 5 – OVERDRIVE (OD)

Overdrive Control Input

⚠️ This wire is an input, not an output.

This wire is used to bring the vehicle’s existing overdrive control signal into the ECU / transmission control logic.

Function:

• Allows      the vehicle’s overdrive switch to command whether overdrive is enabled or      cancelled
• Used      to determine whether 4th gear is permitted

Operation:

• When      connected correctly to the existing overdrive switch circuit, the ECU can      recognize overdrive enable / cancel status
• This      is not a dash output and does not supply power to an indicator

Installation Notes:

• Connect      this wire to the vehicle’s existing overdrive switch circuit
• The      exact switching method must match the switch arrangement being used on the      vehicle
• Incorrect      wiring of this circuit may result in:
  • No       overdrive operation
  • Overdrive       permanently enabled
  • Overdrive       permanently cancelled
  • Incorrect       shifter behavior

Important:

This circuit is a control input only and must not be treated as a gear-position output.

Pin 6 – SECOND (2)

12V Output – 2nd Gear Range Indicator

This wire outputs +12V when the transmission is in 2 range.

Function:

• Used      to indicate that the transmission has been manually restricted to the 2      position
• Used      for cluster / dash indication where applicable

Operation:

• Transmission      in 2: wire outputs +12V
• Any      other gear selected: no output

Installation Notes:

• Low-current      output for signal / indicator use only

Pin 7 – LOW (L / 1)

12V Output – Low Gear Indicator

This wire outputs +12V when the transmission is in Low.

Function:

• Used      to indicate Low gear selection
• Used      for cluster / dash indication where applicable

Operation:

• Transmission      in Low: wire outputs +12V
• Any      other gear selected: no output

Installation Notes:

• Low-current      output for signal / indicator use only

Pin 8 – CCS

Cruise Control Switch Input (Resistance-Based Signal)

This is a resistance-based input from the Toyota cruise control lever.

Function:

This circuit allows multiple cruise-control commands to be sent to the ECU using a single wire.

How This Circuit Works:

Toyota supplies battery voltage to the cruise control switch, and the ECU monitors the CCS terminal voltage according to switch position. The switch changes the circuit by applying different resistance values for the different lever functions.

Typical Toyota Resistance Values:

• Main      switch ON: below 1 Ω
• Main      switch OFF: 10 kΩ     or higher
• RES      / ACC: 235 to 245 Ω
• SET      / COAST: 617 to 643 Ω
• CANCEL:      1,509 to 1,572 Ω

Typical ECU Voltage Checks:

With ignition ON, Toyota’s ECU terminal checks for this switch family show:

• Switch      at rest: 10 to 14 V
• CANCEL:      6.6 to 10.1 V
• SET      / COAST: 4.5 to 7.1 V
• RES      / ACC: 2.3 to 4.0 V
• Main      ON/OFF button pressed: below 1 V

Important:

This is not a simple switched 12V input and it is not a simple ground trigger.

If the wrong cruise lever is used, or if the resistance values do not match what the ECU expects, common problems may include:

• Cruise      control not engaging
• Incorrect      cruise function being triggered
• Intermittent      cruise operation
• Fault      codes

Testing Notes:

• Resistance      can be measured through the switch while moving the lever through each      function
• Voltage      can also be measured at the ECU input and compared to the Toyota      terminal-check values above
• Poor      connections, corrosion, or added resistance in the circuit can affect      operation

⚠️ Important:
Do not apply direct +12V or direct ground to this circuit unless the switch design specifically requires it.
This is a low-current resistance-based signal input.

Pin 9 – STP

Brake Pedal Input – Normally Open (NO) Brake Switch Circuit

This wire must be connected to the normally open side of the brake light switch.

Function:

• Provides      the ECU with the primary brake application signal
• Used      to cancel cruise control immediately when the brake pedal is pressed

Operation:

• Brake      pedal released: no voltage present on STP
• Brake      pedal pressed: STP receives +12V

Toyota ECU Check:

Toyota’s ECU terminal check for this circuit shows:

• Brake      released: below 1 V
• Brake      depressed: 10 to 14 V

Installation Notes:

• Connect      STP to the same side of the brake switch that becomes live when the pedal      is pressed
• This      is normally the same circuit that feeds the brake lamps

Important:

If STP is not connected correctly, cruise control may:

• Fail      to engage
• Fail      to cancel correctly
• Set      an input fault

Pin 10 – ST1-

Brake Pedal Input – Normally Closed (NC) Brake Switch Circuit

This wire must be connected to the normally closed side of the brake switch.

Function:

• Provides      the ECU with a secondary brake status signal
• Used      for cruise-control safety validation

Operation:

• Brake      pedal released: ST1- remains live through the normally closed circuit
• Brake      pedal pressed: the circuit opens and the signal changes state

Toyota ECU Check:

Toyota’s ECU terminal check for this circuit shows:

• Brake      released: 10 to 14 V
• Brake      depressed: below 1 V

Why This Circuit Matters:

The ECU compares STP and ST1- to confirm that the brake switch is working correctly.

This gives the ECU two opposite brake signals:

• STP      goes high when the brake is pressed
• ST1-      goes low when the brake is pressed

If these signals do not agree, cruise control may be disabled or may not function correctly.

Installation Notes:

• The      brake switch being used must provide both:
  • A       normally open contact for STP
  • A       normally closed contact for ST1-
• If      the brake switch does not provide both contacts, cruise control logic may      not function correctly

Pin 11 – __________________

Additional / Application-Specific Function

Use this space to add any additional pin assignment specific to the individual harness build.

Pin 12 – __________________

Additional / Application-Specific Function

Use this space to add any additional pin assignment specific to the individual harness build.

⚠️ GEAR OUTPUT NOTES

• Park,      Reverse, Neutral, Drive, 2, and Low are 12V outputs
• These      outputs are intended for indicator / interface purposes
• They      are low-current outputs
• Only      the appropriate gear-position signal should be active for the gear      selected
• Do      not use these outputs to directly power high-current devices unless the      receiving circuit and load are known to be suitable

⚠️ CRUISE CONTROL IMPORTANT NOTES

For proper cruise-control operation:

• CCS      must be connected to the correct Toyota / Lexus style resistance-based      cruise switch
• STP      must be connected to the normally open brake switch circuit
• ST1-      must be connected to the normally closed brake switch circuit

Incorrect wiring may result in:

• Cruise      not engaging
• Cruise      not cancelling
• Incorrect      cruise switch operation
• Fault      codes
• Unreliable      cruise behavior

🔧 INSTALLATION NOTES

✔ Gear Position Verification

• Cycle      the shifter through all positions
• Verify      the correct gear output becomes active in each position
• Confirm      the cluster displays the correct range where applicable

✔ Reverse Circuit

• If      using the Reverse output to operate reverse lights, verify current draw      and use a relay where required

✔ Overdrive Circuit

• Confirm      correct operation of the overdrive switch after installation
• Verify      overdrive can be enabled and cancelled correctly

✔ Cruise Control Verification

• Verify      STP and ST1- change state correctly with brake pedal movement
• Verify      CCS values or ECU input voltages change correctly as the cruise lever is      moved

✔ Grounding

• Ensure      engine and chassis grounds are solid
• Poor      grounding can cause signal problems and incorrect operation

⚠️ IMPORTANT

• All      circuits in this connector are intended as signal / interface circuits
• Do      not use these wires to power unrelated accessories
• Do      not apply power to input circuits unless specified
• Verify      all wiring before final power-up

🧠 SYSTEM SUMMARY

This 12-pin connector provides the 4 speed automatic interface for:

• Gear      indication outputs
• Overdrive      control input
• Cruise-control      switch input
• Brake-switch      cruise-control inputs
• Cluster      / dash integration

🚗 FINAL NOTE

When installed correctly, this system will:

• Provide      accurate gear indication
• Interface      correctly with the vehicle cluster
• Allow      proper overdrive input function
• Enable      safe and reliable cruise-control operation