Toyota Tundra Service Manual: System Description

SYSTEM DESCRIPTION

1. DESCRIPTION

  • A part-time 2-speed WF1AM transfer uses a touch select 2-4 and high-low system, enabling the driver to switch between 2WD, 4H and 4L modes by turning the transfer position switch.
  • Through these switch signals, the 4 wheel drive control ECU actuates the shift motor in the transfer shift actuator and another shift motor in the A.D.D. actuator (differential vacuum actuator assembly).

2. DRIVING MODE SWITCHING PATTERN

Text in Illustration

*1

Transfer Position Switch

-

-

3. INDICATOR LIGHT AND WARNING BUZZER OPERATING CONDITIONS

Mode

4HI Indicator Light

4LO Indicator Light

Warning Buzzer

2WD

Not illuminated

Not illuminated

Not sounding

Switching from 2WD to 4H

Blinking

Not illuminated

Not sounding

2WD to 4L switch request (not permitted)

Blinking

Not illuminated

Sounding

4H

Illuminated

Not illuminated

Not sounding

Switching from 4H to 2WD

Blinking

Not illuminated

Not sounding

Switching from 4H to 4L

Illuminated

Blinking

Not sounding

4H to 4L switch request (not permitted)

Illuminated

Blinking

Sounding

4L

Not illuminated

Illuminated

Not sounding

Switching from 4L to 2WD

Blinking

Illuminated

Not sounding

4L to 2WD switch request (not permitted)

Blinking

Illuminated

Sounding

Switching from 4L to 4H

Blinking

Illuminated

Not sounding

Malfunctioning

Rapidly blinking

Rapidly blinking

Not sounding

  • Blinking: Blinks at 0.5 second intervals (0.5 seconds on and 0.5 seconds off)
  • Rapidly blinking: Blinks at 0.25 second intervals (0.25 seconds on and 0.25 seconds off)

4. FUNCTION OF COMPONENTS

Components

Functions

Transfer position switch

Allows switching between the 3 drive modes: 2WD, 4HI and 4LO.

Combination meter assembly

4HI indicator light

Illuminates to inform the user of 4HI mode status.

Blinks to inform the user of mode switching.

Rapidly blinks to inform the user of a system malfunction.

4LO indicator light

Illuminates to inform the user of 4LO mode status.

Blinks to inform the user of mode switching.

Rapidly blinks to inform the user of a system malfunction.

Warning buzzer

Sounds an alarm if a violation of the conditions required for mode shifting occurs when the transfer mode is shifted.

Skid control ECU

Outputs wheel speed signals to the 4 wheel drive control ECU via CAN communication.

Speed sensors

Detects the speeds of all 4 wheels and sends that information to the skid control ECU.

ECM

Outputs information such as the shift lever position and engine speed to the 4 wheel drive control ECU via CAN communication.

Park/neutral position switch

Detects the shift lever position and sends that information to the ECM.

4 wheel drive control ECU

Determines the vehicle status from wheel and engine speed signals received via CAN communication, and according to the operation of the transfer position switch, switches to the requested 4WD mode by operating the transfer shift actuator assembly.

Transfer shift actuator assembly

Operates the transfer shift motor according to commands sent from the 4 wheel drive control ECU and switches to 4WD mode.

Transfer indicator switch

Detects the 2WD, 4HI and 4LO positions and sends that information to the 4 wheel drive control ECU.

A.D.D. actuator (differential vacuum actuator assembly)

A.D.D. shift motor and limit switch

Operates the A.D.D. shift motor according to commands sent from the 4 wheel drive control ECU and switches between 2WD and 4WD.

A.D.D. detection switch

Detects the 2WD and 4WD A.D.D. positions and sends that information to the 4 wheel drive control ECU.

  • Blinking: Blinks at 0.5 second intervals (0.5 seconds on and 0.5 seconds off)
  • Rapidly blinking: Blinks at 0.25 second intervals (0.25 seconds on and 0.25 seconds off)
    Shift Motor Circuit

    System Diagram

    See More:

    Toyota Tundra Owners Manual > For safe use: Installing child restraints
    Follow the child restraint system manufacturer's instructions. Firmly secure child restraints to the seats using the LATCH anchors or a seat belt. Attach the top tether strap when installing a child restraint. The lap/shoulder belt can be used if your child restraint system is not compatible with t ...

    Toyota Tundra Owners Manual

    Toyota Tundra Service Manual

    © 2021 Copyright www.ttundra.com
    0.0146