Toyota Repair Problems? Ask a Mechanic for Answers ASAP
Your's is the only resposnse that i have had. Seems like the question is too hard.
I believe that there is a cruise control module required, but I cannot find any wiring diagrams that display cruise control module and how it is connected to the ECU and accelerator wires.
Also, I expect there will be a different module part number for each engine type/transmission.
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Since this vehicle is a drive by wire throttle body system, the only thing that is needed to add cruise control to your vehicle is the switch (mounted in the factory location) and a software adjustment in the engine computer.
The engine computer must be programmed with the correct software so it can accept and identify the inputs from the cruise control switch. Additionally, the engine computer software must have the capabilities to calculate the throttle control from the vehicle speed to make the cruise work. Then, the disabling factors from the brake switch inputs, accelerate, resume...
Your current vehicle has computer software for no cruise control
Once the switch is installed and the computer software reprogrammed for a vehicle with cruise control, your goal will be a success.
The software will perform the following functions:
SYSTEM DESCRIPTION 1. CRUISE CONTROL SYSTEM The cruise control system makes it possible to drive at a desired speed without using the accelerator pedal. The ECM controls the throttle opening angle based on signals from switches and sensors. A microcomputer which controls the cruise control system is built into the ECM, and the actuator is the throttle body assy (intake shutter assy). Constant speed control is ready to operate when the cruise control main switch ON-OFF button is pushed (the CRUISE main indicator light comes on). Operating the cruise control main switch, the driver can control the following functions. 2. LIMIT CONTROL a. Low speed limit The lowest possible limit of the speed setting range is set at approximately 40 km/h (25 mph). The cruise control system cannot be set when the driving vehicle speed is below the low speed limit. Cruise control operation will be automatically canceled and the stored vehicle speed will be erased when the vehicle speed goes below the low speed limit while the cruise control is in operation. b. High speed limit The highest possible limit of the speed setting range is set at approximately 200 km/h (125 mph). The cruise control system cannot be set when the driving vehicle speed is over the high speed limit. Speed up using "RES/ACC" with the cruise control main switch assy also cannot be set beyond the high speed limit. 3. OPERATION OF CRUISE CONTROL The cruise control main switch operates seven functions: SET, COAST, TAP-DOWN, ACCEL, TAP-UP, RESUME and CANCEL. The SET, TAP-DOWN and COAST functions, and the RESUME, TAP-UP and ACCEL functions are operated with the same switch. The cruise control main switch assy is an automatic return type switch which turns on only while operating it in each arrow direction and turns off after releasing it. a. SET CONTROL When pushing down the cruise control main switch to "SET/COAST", the ECM stores the set speed and compares it to actual vehicle speed. If the actual driving speed is greater than the set speed, the ECM sends a signal to the throttle body assy (intake shutter assy) to close the throttle valve. If lower, it opens the throttle valve. The cruise control operative speed range is between the low and high speed limits. b. COAST CONTROL A cruise set speed decreases while pushing down on the cruise control main switch to "SET/COAST". The vehicle cruises at the newly set speed when releasing the cruise control main switch. c. TAP-DOWN CONTROL When tapping down on the cruise control main switch to "SET/COAST" (approximately 0.5 second), the ECM decreases the stored set speed by 1.6 km/h (1 mph) at a time. However, when the difference between the driving and the stored vehicle speed is more than 5 km/h (approximately 3.1 mph), vehicle speed, when the cruise control main switch is released from "SET/COAST", will be stored and constant speed control is maintained. d. ACCEL CONTROL A cruise set speed increases while pushing up on the cruise control main switch to "RES/ACC". The vehicle cruises at the newly set speed when releasing the cruise control main switch. e. TAP-UP CONTROL When tapping up on the cruise control main switch to "RES/ACC" (approximately 0.5 second), the ECM increases the stored set speed by 1.6 km/h (1 mph) at a time. However, when the difference between the driving and the stored vehicle speed is more than 5 km/h (approximately 3.1 mph), the stored vehicle speed will not be changed. f. RESUME CONTROL If cruise control operation was canceled under the manual cancel conditions (other than pushing the cruise control main switch ON-OFF button off), and if driving speed is within the limit range, pushing up the cruise control main switch to "RES/ACC" restores vehicle speed memorized at the time of cancellation, and maintains constant speed control. g. MANUAL CANCEL CONTROL The ECM cancels the cruise control under the following conditions while driving: - The cruise control main switch is pulled to CANCEL. - The brake pedal is depressed. - The clutch pedal is depressed (Manual Transaxle). - Moving the shift lever to the any position except D (Automatic transaxle). - The cruise control main switch ON-OFF button is pushed off. h. AUTO CANCEL CONTROL If any of the following malfunctions occur in the system, the ECM stops the cruise control until the cruise control main switch ON-OFF button is pushed off. - Stop lamp switch assy malfunction - Vehicle speed signal circuit malfunction - Throttle position sensor and motor malfunction If any of the following malfunctions occur in the system, the ECM stops the cruise control until the ignition switch is turned off. - Stop lamp switch input circuit malfunction - CANCEL function circuit malfunction Under these conditions, the cruise main indicator light blinks until the cruise control main switch ON-OFF button is pushed off. AUTO CANCEL also works when actual vehicle speed either drops below 40 km/h (25 mph) or is 16 km/h lower than the set speed. i. OTHERS CANCEL CONTROL Cruise control will be halted if VSC starts operation while driving (vehicle speed will be memorized).
Hello, your response is quite lengthy, however, most of it I already know. Back to the physical connection. There are wires that will be needed to connect the steering wheel control to the ECU. Previous vehicles have aalso had separate switches for brake pedal, and gear-selector. I assume that all these will need to be connected somewhere.
I woud like a circuit diagram of the wiring involved.
Your concerns are quite common and difficult to explain.
The first thing that will need to be understood is that the computers are all linked together.
Each computer, engine, body, airbag, braking system, instrument, lighting... all these computers are linked together and share information on a network system.
For instance... the brake module will take an input of the brake switch and send the information regarding this switch on a data wire to the engine, lighting, body, and other modules which request and/or need an initial information change regarding this switch/sensor.
So, actual physical connections for every switch are already there at each computer.
The only connection that this vehicle will need is the connection from the cruise control switch to the engine control module.
Then, the ECM will need to have the software re programed to acknowledge and control the cruise as needed. The brake switch and all the other switches and sensors are already there. There is no cruise servo, no TPS, speed, brake, clutch or any other connections to be made. They are already there and all the appropriate modules know the information.
The connector for the cruise switch should be already there. However, if for some reason it is not, then the wires to the appropriate connectors to the ECM will need to be made. But only the wires for the switch.
Thankyou, You have now clarrified the situation for me. Seems I will still have to get Toyota to implement a firmware upgrade to activate the Cruise Control. Hope that they will be cooperative.
One final question, Are the "clock-springs" all the same?
If the switch is mounted on the steering wheel then the clock spring will be different unless the vehicle is built as a general export. Basically, if you have found a plug on the steering wheel to accept the switch then the clock spring will be the same. If not, then the clock spring will need to be changed as well.