Toyota Tundra Service Manual: System Description

Toyota Tundra Service Manual / Engine, Hybrid System / Wf1am Transfer / Touch Select 2-4 And High-low System / 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

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. actuator (differential vacuum actuator assembly)	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)

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Toyota Tundra Service Manual: System Description

Shift Motor Circuit

System Diagram

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