Oem System Circuits: Other Scion xB II

Relay Blocks

Ground Points

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System Outline

The engine control system utilizes a microcomputer and maintains overall control of the engine, transmission etc. An outline of the engine control is given here.

1. Input Signals Engine coolant temperature signal circuit The engine coolant temperature sensor detects the engine coolant temperature and has a built-in thermistor with a resistance which varies according to the engine coolant temperature. The engine coolant temperature is input into TERMINAL THW of the engine control module as a control signal. Intake air temperature signal circuit The intake air temperature sensor is installed in the mass air flow meter and detects the intake air temperature which is input as a control signal to TERMINAL THA of the engine control module. Vehicle speed signal circuit The vehicle speed signal is input from the speed sensor to the skid control ECU with actuator, and is sent to the engine control module through communication control. RPM signal circuit The engine RPM is detected by the crankshaft position sensor installed in the cylinder block and the signal is input into TERMINAL NE+ of the engine control module as a control signal. Throttle position signal circuit The throttle position sensor detects the throttle valve opening angle as a control signal, which is input into TERMINALS VTA1 and VTA2 of the engine control module. Battery signal circuit Voltage is constantly applied to TERMINAL BATT of the engine control module. When the ignition Switch is turned on, the voltage for engine control module start-up power supply is applied to TERMINALS +B and +B2 of the engine control module via the EFI MAIN relay. The current flowing through the IGN fuse flows to TERMINAL IGSW of the engine control module. Intake air volume signal circuit Intake air volume is detected by the mass air flow meter and the signal is input to TERMINAL VG of the engine control module as a control signal. Stop light switch signal circuit The stop light switch is used to detect whether the vehicle is braking or not and the signal is input into TERMINAL STP of the engine control module as a control signal. Starter signal circuit To confirm whether the engine is cranking, the voltage which is being applied to the starter motor during cranking is detected and the signal is input into TERMINAL STA of the engine control module as a control signal. Engine knock signal circuit Engine knocking is detected by knock sensor and the signal is input into TERMINAL KNK1 as a control signal. Air fuel ratio signal system The air fuel ratio is detected and input as a control signal into TERMINAL A1A+ of the engine control module. Oxygen sensor signal circuit The oxygen density in the exhaust gases is detected and input as a control signal into TERMINAL OX1B of the engine control module. To maintain stable detection performance by the heated oxygen sensor, a heater is used for warning the sensor. The heater is also controlled by engine control module.
2. Control System * SFI system The SFI system monitors the engine condition through the signals received from various sensors by the engine control module. And then control signals are output from TERMINALS #10, #20, #30 and #40 of the engine control module to operate the injectors (Inject the fuel). The SFI system controls the fuel injection operation for the engine control module in response to the driving conditions. * ESA system The ESA system monitors the engine condition through the signals received by the engine control module from various sensors. The best ignition timing is decided according to this data and the data stored in the engine control module and the control signals are output from TERMINALS IGT1, IGT2, IGT3 and IGT4. These signals control the igniters to provide the best ignition timing for the driving conditions.
3. Diagnosis System With the diagnosis system, when there is a malfunction in the engine control module signal system, the malfunctioning system is recorded in the memory. The malfunctioning system can be found by reading the code displayed by the malfunction indicator lamp.
4. Fail-safe System When a malfunction has occurred in any system, if there is a possibility of engine trouble being caused by continued control based on the signals from that system, the fail-safe system either controls the system by using data (Standard values) recorded in the engine control module memory or else stops the engine.

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Previous automatic transmissions have selected each gear shift using mechanically controlled throttle hydraulic pressure, governor hydraulic pressure and lockup hydraulic pressure. The electronically controlled transmission, however, controls the line pressure, throttle pressure, lockup pressure and accumulator pressure etc. electrically via the solenoid valve. The electronically controlled transmission is a system which precisely controls gear shift timing and lockup timing in response to the vehicle driving conditions and the engine conditions detected by various sensors. It makes smooth driving possible by selecting the gear which is most appropriate to the driving conditions at that time, and by preventing downing, squat and gear shift shock when starting off.

1. Gear Shift Operation When driving, the engine warm up condition is sent as a signal to TERMINAL THW of the engine control module from the engine coolant temp. sensor, and the vehicle speed signals from the speed sensors are sent to the skid control ECU with actuator, and are sent to the engine control module through communication control. At the same time, the throttle valve opening signal is sent from the throttle position sensor to the TERMINALS VTA1 and VTA2 of the engine control module, as the throttle angle signal.
2. Lock-Up Operation If the engine control module decides, based on the received signals, that the lock-up condition has been met, the current flows through TERMINAL DSL of the engine control module to TERMINAL 3 of the electronically controlled transmission solenoid to GROUND.
3. Stop Light Switch Circuit If the brake pedal is depressed (Stop light switch on) while driving in lock-up condition, a signal is input to TERMINAL STP of the engine control module. The engine control module operates and cuts the current to the solenoid to release the lock-up.

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The cruise control system is a constant vehicle speed controller in which control of the switch on the instrument panel makes it possible to automatically adjust the opening of the engine throttle valve without depressing the accel pedal.

1. Set Control If the - SET switch is pressed while driving with the ON-OFF switch ON, the vehicle speed at that time is registered and the vehicle is maintained at that speed.
2. Coast Control If the - SET switch is held down while driving with the cruise control active, the cruise control required opening gets set to zero to reduce the vehicle speed. If the - SET switch is released, the vehicle speed at that time is registered and the vehicle is maintained at that speed.
3. Tap Up Control Whenever + RES switch is pressed briefly (For approximately 0.6 sec.), the registered vehicle speed increases by about 1.6 km/h (1 mph).
4. Tap Down Control Whenever the - SET switch is pressed briefly (For approximately 0.6 sec.), the registered vehicle speed decreased by about 1.6 km/h (1 mph).
5. Accel Control If the + RES switch is held down while driving with the cruise control active, the engine control module adjusts the throttle valve to accelerate the vehicle. It also registers the vehicle speed when the + RES switch is released and maintains the vehicle at that speed.
6. Manual Cancel Mechanism If any of the following signals is received while driving with the cruise control active, the cruise control will be cancelled. * The stop lamp switch is turned on. * The CANCEL switch is turned on. * The ON-OFF switch is turned off. * The clutch pedal is depressed. * The transmission is shifted from "D" to "N". (When shifted to 1 or 2 in sequential shift mode.)
7. Auto Cancel Function If any of the following conditions is encountered, the cruise control will be automatically cancelled. * The stop light switch wiring is faulty or short-circuited. * The vehicle speed signal is faulty. * The electronically controlled throttle malfunctions. * The actual vehicle speed falls to 16 km/h (10 mph) slower than the set speed. * The actual vehicle speed falls to a speed slower than the minimum speed limit.
8. Other Function If any of the VSC systems activate, the cruise control will be cancelled. When the ignition switch is turned off, the set speed will be automatically deleted.
9. Overdrive Control Function The overdrive control may be cancelled if the vehicle travels on a slope while driving with the cruise control active. After the overdrive control has been cancelled, and when the hill is judged to have finished (from throttle opening information), the vehicle returns to the overdrive control mode again after the overdrive return timer has expired.

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* When the driver's door is opened (Front door courtesy switch LH : ON) while the key is still inserted in the ignition key cylinder (Unlock warning switch : ON) and the ignition switch is OFF (LOCK), the main body ECU sends signals to the combination meter through CAN communication. The meter computer responds to the signals by sounding the multi buzzer intermittently in order to warn the driver that the ignition key has not been removed.

* The buzzer stops when the ignition switch is turned ON, the driver's door is closed or the key is pulled out.

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1. ABS Operation If the brake pedal is depressed suddenly, the ABS controls the hydraulic pressure of the wheel cylinders for all four of the wheels to automatically prevent the wheels from locking and ensure the directional and steering stability of the vehicle. If the brake pedal is depressed suddenly, the skid control ECU controls the solenoids in the actuators using the signals from the brake sensors to move the brake fluid to the reservoir in order to release the braking pressure being applied to the wheel cylinders. If the skid control ECU detects that the fluid pressure in the wheel cylinder is insufficient, the ECU controls the solenoids in the actuators to increase the braking pressure.
2. Traction Control Operation The traction control system controls the engine torque, the hydraulic pressure of the driving wheel cylinders, and any wheel slippage which may occur at take off or when accelerating the vehicle, to optimize the driving power and vehicle stability to match the road conditions.
3. VSC Operation Unexpected road conditions, vehicle speed, emergency situations, and any other external factors may cause large under- or over-steering of the vehicle. If this occurs, the VSC system automatically controls the engine power and wheel brakes to reduce the under- or over-steering. To reduce large over-steer : If the VSC system determines that the over-steer is large, it activates the brakes for the outer turning wheels depending on the degree of the over-steer to produce the moment toward the outside of the vehicle and reduce the over-steer. To reduce large under-steer: If the VSC system determines that the under-steer is large, it controls the engine power and activates the rear wheel brakes to reduce the under-steer.
4. Fail Safe Function If an error occurs in the skid control ECU with Actuator, sensor signals, and/or actuators, the skid control ECU with Actuator inhibits the brake actuator control and sends an error signal to the engine control module. According to the error signal, the brake actuator turns off the solenoid and the engine control module rejects any electronically controlled throttle open request from the VSC system. As a result, the vehicle functions regardless of the ABS, TRAC, and VSC systems.

SRS

Note. When inspecting or repairing the SRS, perform service in accordance with the following precautionary instructions and the procedure, and precautions in the service information applicable for the model year.

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1. Malfunction symptoms of the SRS are difficult to confirm, so the DTCs become the most important source of information when troubleshooting. When troubleshooting the SRS, always inspect the DTCs before disconnecting the battery.
2. Work must be started more than 90 seconds after the ignition switch is turned to the "LOCK" position and the negative (-) terminal cable is disconnected from the battery. (The SRS is equipped with a back-up power source so that if work is started within 90 seconds from disconnecting the negative (-) terminal cable of the battery, the SRS may deploy.)
3. When the negative (-) terminal cable is disconnected from the battery, the memory of the clock and audio system will be cleared. So before starting work, make a record of the contents in the audio memory system. When work is finished, reset the audio systems as they were before and adjust the clock. Some vehicles have power tilt steering, power telescopic steering, power seat and power outside rear view mirror which are all equipped with memory function. However, it is not possible to make a record of these memory contents. So when the work is finished, it will be necessary to explain it to your customer, and ask the customer to adjust the features and reset the memory. To avoid erasing the memory in each system, never use a back-up power supply from outside the vehicle.
4. Before repair, remove the airbag sensor if shocks are likely to be applied to the sensor during repair.
5. Do not expose the following parts directly to hot air or flame
6. Even in cases of a minor collision where the SRS does not deploy, the following parts should be inspected
7. Never use SRS parts from another vehicle. When replacing parts, replace with new parts.
8. For the purpose of reuse, never disassemble and repair the following parts.
9. If the following parts have been dropped, or have cracks, dents and other defects in their case, bracket, and connector, replace with new one.
10. Use a volt/ohmmeter with high impedance (10 kohms/V minimum) for troubleshooting electrical circuits of the system.
11. Information labels are attached to the periphery of the SRS components. Follow the instructions of the notice.
12. After work on the SRS is completed, check the SRS warning light.
13. If the vehicle is equipped with a mobile communication system, refer to INTRODUCTION .

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* The system reaches an ignition judgment to deploy the following devices based on the signals received from the front airbag sensor and deceleration sensor.

1. Driver Airbag
2. Front Passenger Airbag
3. Seat Belt Pretensioner

* The system reaches an ignition judgment to deploy the following devices based on the signals received from the side airbag sensors.

1. Side Airbags
2. Curtain Shield Airbags

* The dual-stage SRS airbag system has been used for the driver and front passenger airbags. This system optimizes the airbag inflation by judging the extent of impact, seat position (driver seat) and whether or not the seat belt is fastened (driver seat) and information from the Front Passenger Occupant Classification System.

* The front passenger occupant classification system judges whether the front passenger seat is occupied by an adult or child (with child seat) or is unoccupied, according to the load applied to the front passenger seat, seat position (passenger), the load applied to the belt tension sensor (passenger), and whether the seat belt is buckled (passenger). Based on the results, it restricts the deployment of the front passenger airbag, front passenger side airbag, and front passenger seat belt pretensioner. In addition, the system informs the driver of the result of the judgment through the use of the AIRBAG ON/OFF indicator lights.

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* To reduce steering force required by the driver, assist current is calculated from torque sensor signal and vehicle speed signal and output to the motor which provides the assistance.

* When an abnormality is found in the system, the power relay and motor relay (Built in the ECU) are shut off to stop the assistance and the warning lamp (Power Steering) illuminates in the meter.

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1. Manual Lock & Unlock Function All the doors (Excluding the back door) can be locked or unlocked by operating the door lock control switch (For manual operation) to the 'lock' or 'unlock' side.
2. Key Confinement Prevention Function To prevent the key from being left in the cabin, this system prevents the door lock control switch (For manual operation or for key-linked) or the door lock knob from locking any of the doors if the key is still in the ignition key cylinder when the driver's door is open.
3. Door Lock Security Function When a lock operation is activated via the wireless remote control and so on, the door security function is set to prevent the door lock control switch from unlocking any of the doors.
4. Door Key Unlock Operation * Unlock operation from driver's side door If the driver's side door is unlocked once using the ignition key, only the driver's side door will be unlocked. If this operation is repeated within 3 seconds, all the remaining doors will be unlocked.

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1. Wireless Lock & Unlock Function Pushing the lock button locks all the doors and pushing the unlock button unlocks the all the doors.
2. 60-Second Auto Lock Function If none of the door are opened within 60 seconds after they are unlocked with the unlock button, all the doors are locked automatically again to prevent the doors from being left open.
3. Answer Back Function (Hazard Light Flashing) The hazard light flashes once when locking, and flashes twice when unlocking if the doors are locked/unlocked through the wireless remote control.

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