Toyota Tundra Service Manual: System Description

SYSTEM DESCRIPTION

GENERAL

The cruise control system is controlled by the ECM, and vehicle speed control is performed using the throttle body with motor assembly. The ECM controls the following functions: ON-OFF, - (COAST)/SET, + (ACCEL)/RES (RESUME), CANCEL, vehicle speed operation and shift down control.

  • The ECM compares the vehicle speed from the speed sensors with the stored vehicle speed set using the cruise control main switch. The ECM increases the opening angle of the throttle valve when the actual vehicle speed is below the stored vehicle speed, and decreases the opening angle of the throttle body when the actual vehicle speed is more than the stored vehicle speed.
  • The ECM receives signals such as ON-OFF, - (COAST)/SET, + (ACCEL)/RES (RESUME), and CANCEL signals from the cruise control main switch.
  • The ECM illuminates the cruise control indicator in the combination meter assembly when the cruise control system is turned on using the cruise control main switch (ON-OFF button).
  • The ECM turns off the cruise control indicator in the combination meter assembly and displays a warning message if a malfunction is detected when the cruise control system is controlling vehicle speed.
  • The ECM illuminates the cruise control SET indicator in the combination meter assembly when vehicle speed control begins after the cruise control main switch is pushed to -SET while driving. Also, the ECM displays the current set speed on the multi-information display when the cruise control main switch is pushed to +RES or -SET.

    *1

    Cruise Control Indicator

    *2

    Cruise Control SET Indicator

FUNCTION OF MAIN COMPONENTS

(a) The main components of the cruise control system have the following functions:

Component

Function

Cruise Control Main Switch

ON-OFF Button

Turns the cruise control system on and off.

CANCEL Switch

A cancel signal is sent to the ECM when the switch is operated.

+RES Switch

Acceleration and stored speed resume signals are sent to the ECM when the switch is operated.

-SET Switch

Deceleration and vehicle speed setting signals are sent to the ECM when the switch is operated.

Skid Control ECU (Brake Actuator Assembly)

  • Sends VSC operation signals to the ECM.
  • Sends TRAC operation signals to the ECM.
  • Sends signals such as wheel speed and estimated vehicle acceleration signals to the ECM.

ECM

Controls all functions of the cruise control system in accordance with the signals received from switches, sensors and ECUs.

Combination Meter Assembly

Cruise Control Indicator

  • Illuminates based on signals from the ECM when the cruise control system is turned on using the cruise control main switch (ON-OFF button).
  • Turns off based on signals from the ECM when a malfunction is detected in the cruise control system.

Cruise Control SET Indicator

Illuminates when the vehicle speed is set.

Multi-information Display

  • Displays warning messages to alert the driver.
  • Displays the current set speed.

Throttle with Motor Body Assembly

Throttle Control Motor

Adjusts the throttle valve opening angle in accordance with signals received from the ECM.

Throttle Position Sensor

Outputs the throttle valve opening angle to the ECM.

Speed Sensor

Outputs wheel speed signals to the skid control ECU.

Accelerator Pedal Sensor Assembly

Outputs accelerator pedal depression angle to the ECM.

Park/Neutral Position Switch Assembly

Outputs the shift lever position to the ECM.

VSC OFF Switch

Outputs VSC off signals to the skid control ECU.

Stop Light Switch Assembly

Outputs brake pedal depressed signals to the ECM.

Trailer Brake Control ECU (Brake Control with Bracket Relay)*

Detects manual trailer brake output slider operations when towing a trailer.

*: for Trailer Brake Control System

OPERATION OF CRUISE CONTROL

(a) The cruise control system has the following control functions:

Function

Outline

Constant Speed Control

The ECM compares the actual vehicle speed and the set speed and if the vehicle speed is less than the set speed, it uses the throttle control motor to increase the throttle valve opening angle.

Set Control

The vehicle speed is stored and speed control is performed when the cruise control main switch is pushed to -SET while driving with the cruise control system on and the vehicle speed is within the set speed range. The current set speed is displayed on the multi-information display when the cruise control main switch is pushed to +RES or -SET.

Low Speed Limit Control

The low speed limit is the lowest speed that cruise control can be set at and it is designed to be approximately 40 km/h (25 mph). The cruise control system cannot be set below that speed. If the vehicle speed drops below that speed while the cruise control is operating, speed control by the cruise control system will be canceled automatically. However, the set speed is kept in memory.

High Speed Limit Control

The highest possible set speed is approximately 200 km/h (125 mph). The cruise control system cannot be set when the vehicle speed is over the high speed limit. Also, + (ACCEL)/RES (RESUME) cannot be used to increase the speed beyond the high speed limit.

- (COAST) Control

When the cruise control system is controlling vehicle speed and the cruise control main switch is pushed to -SET and held in that position, the cruise control system sends a "throttle valve opening angle 0°" demand signal to the ECM. Following this, the vehicle speed is stored and maintained when the cruise control main switch is released.

Tap-down Control

When the cruise control system is controlling vehicle speed and the cruise control main switch is tapped to -SET (for approximately 0.6 seconds), the stored vehicle speed decreases by approximately 1 km/h or 1 mph for each time the switch is tapped. When the cruise control main switch is tapped to -SET and the difference between the current and stored vehicle speed is more than 5 km/h (3 mph), the current vehicle speed is stored and speed control is performed.

+ (ACCEL) Control

When the cruise control system is controlling vehicle speed and the cruise control main switch is pushed to +RES and held in that position, the cruise control system sends a signal to the ECM to operate the throttle valve motor of the throttle body with motor assembly to open the throttle valve. Following this, the vehicle speed is stored and maintained when the cruise control main switch is released.

Tap-up Control

When the cruise control system is controlling vehicle speed and the cruise control main switch is tapped to +RES (for approximately 0.6 seconds), the stored vehicle speed increases by approximately 1 km/h or 1.0 mph for each time the switch is tapped. When the cruise control main switch is tapped to +RES and the difference between the current and stored vehicle speed is more than 5 km/h (3 mph), the stored vehicle speed will not be changed.

RES (Resume) Control

If control of vehicle speed by the cruise control system was canceled due to any of the manual cancel conditions (other than turning the cruise control system off using the cruise control main switch (ON-OFF button)), and if the vehicle speed is between the low and high speed limits, the stored vehicle speed from the time of cancellation will be resumed and maintained when the cruise control main switch is pushed to +RES.

Shift Down Control

When the vehicle is traveling uphill using cruise control, automatic transmission control may cause the transmission to shift down. During shift down control, when the end of uphill travel is determined, the transmission will shift up after a certain period of time. When the transmission shifts down during the accelerator control or the resume control, the transmission will shift up after the accelerator control or the resume control ends.

Manual Cancel Control

Performing any of the following cancels the cruise control system control of vehicle speed (the stored vehicle speed in the ECM is maintained).

  • Depressing the brake pedal.
  • Moving the shift lever from D or S to any other position.
  • Selecting the 3rd, 2nd or 1st range with the shift position in S.
  • Pulling the cruise control main switch to CANCEL.
  • Turning the cruise control system off using the cruise control main switch (ON-OFF button) (the stored vehicle speed in the ECM is not maintained).
  • The brakes are applied with the manual trailer brake output slider.*

Automatic Cancel Control

This system has an automatic cancellation function (fail-safe).

*: for Trailer Brake Control System

    Road Test

    System Diagram

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