Conventional EFI-diesel

Common-rail EFI-diesel

4. Comparison of the target injection timing and the actual injection timing

As with the convention EFI-diesel, the basic injection timing of the common- rail EFI-diesel is determined through the engine speed and the accelerator pedal opening angle, and by adding a correction value based on the water temperature and the intake air pressure (volume). The ECU sends injection signals to the EDU and advances or retards the timing to adjust the injection starting timing.

Starting Control

Injection Volume Control During Starting

The starting injection volume is determined by adjusting the basic injection volume in accordance with the starter ON signals (ON time) and coolant temperature sensor signals. When the engine is cold, the coolant temperature will be lower and the injection volume will be greater. To determine the starting injection timing is corrected in accordance with the starter signals, water temperature and engine speed. When the water temperature is low, if the engine speed is high, the injection timing is advanced.

Injection Rate Control

Split Injection

A radial plunger type pump performs split injection (two-time injection) when starting the engine at an extremely low temperature (or under -10 degrees) to improve startability and reduce the generation to white and black smoke.

Pilot Injection

The common-rail EFI-diesel uses pilot injection. In the pilot injection system, a small amount of fuel is initially injected before the main injection. When the main injection starts, the fuel that has been injected in advance is already ignited, enabling the fuel of the main injection to ignite smoothly.

Idle Speed Control

Based on the signals from the sensors, the ECU calculates the target speed in accordance with the driving conditions. The ECU then compares the target value with the (engine speed) signal from the engine speed sensor and controls the actuators(SPV/injector) to regulate the injection volume in order to correct the idle speed. The ECU effects idle-up control (in order to improve the engine’s warm-up performance) during fast idle when the engine is cold, or during air conditioner/power heater operations. Also, in order to prevent fluctuations in idle speed caused by a reduction in engine load that occurs when the A/C switch is turned off, the volume is automatically corrected before the engine speed fluctuates.

Idle Vibration Reduction Control

This control detects the fluctuations in the engine speed during idle caused by the variances in the injection pump or nozzles, and corrects the injection volume for each cylinder. Consequently, idle vibration and noise are reduced.

Back-up Function
The back-up function switches over to fixed signal control by the back-up IC to permit driving in cases when a malfunction occurs in the microcomputer inside the engine ECU. The back-up function only controls basic functions, so it is unable to provide the same level of engine performance as when the engine is operating normally.
1. Operation of the back-up function
The engine ECU switches to back-up mode if the microcomputer is unable to output the ignition timing (IGT) signal. When back-up mode is executed, the fuel injection duration and ignition timing are activated at their respective fixed values in response to the starter signal (STA) and IDL signal. The MIL also lights up to inform the driver of a malfunction. (The engine ECU does not record a DTC.)

Fail-safe Function
Purpose of the fail-safe function
If the ECU detects a malfunction in any of the input signal systems, the fail-safe function controls the engine using standard values contained in the engine ECU, or stops the engine to prevent engine problems or catalytic overheating which might occur if control continued based on the circuitry with abnormal signals. The relationship between circuitry with abnormal signals and the fail-safe function is shown in the table below.

DTCs are output as either 5-digit or 2-digit codes. In the Repair Manual, the detection item, detecting condition and trouble area are included for each DTC, so refer to the Repair Manual when troubleshooting.
1. 5-digit DTCs
For 5-digit DTCs, connect the hand-held tester to DLC3 to communicate directly with the engine ECU and display the DTC on the tester screen for confirmation.
2. 2-digit DTCs
Confirm 2-digit DTCs by observing the MIL blinking pattern. Short between terminals TE1 (Tc) – E1 (CG) of DLC1 (Data Link Connector 1), DLC2 or DLC3 to make the MIL blink and output the DTC. Confirm the DTC using the blinking pattern of the lamp.
In the event of tow or more malfunction codes, indication will begin from the smaller numbered code and continue in order to the larger.
To short between the terminals, use the diagnosis check wire (SST: 09843- 18020 or 09843-18040).
HINT:
On some vehicles with DLC3, it is not possible to output 2-digit DTCs.
There are also some models where 2-digit DTCs can be checked using a handheld tester. Connect the hand-held tester to the DLC and read the MIL blinking pattern to confirm the 2-digit DTC on the tester screen.
REFERENCE:
Terminal VF Output
Terminal VF is the terminal that outputs the engine ECU data.
Terminal VF outputs the following data.
1. Air-fuel ratio feedback corrective value
Output is normally fixed at 2.5 V, but a 5 V output provides feedback that the amount of fuel is being increased, so it is possible that the air-fuel ratio has become lean. Conversely, a 0 V output provides feedback that the amount of fuel is being decreased, so it is possible that the air-fuel ratio has become rich. However it is necessary to pay attention for 0 V output when the engine does not meet the conditions of the feedback such as a cold engine.
2. Oxygen sensor signal
When shorted terminals TE1 and E1, and set the throttle position sensor (IDL) contact to off, the output the oxygen sensor signal is 5 V for a rich signal and 0 V for a lean signal. However, if the feedback control is not operating, 0 V is standard.
3. Diagnosis results
When shorted terminal TE1 and E1 (IDL contact is on), 5 V is output if the diagnosis results are normal, or 0 V if a DTC has been stored.
DTC Clear
The engine ECU records DTCs using a constant power supply, so DTCs are not cleared when the ignition switch is turned to off. Accordingly, in order to clear DTCs, it is necessary to use a hand-held tester to communicate with the engine ECU and clear the DTCs, or remove the EFI fuse or battery cable to cut off the constant engine ECU power supply. However, care is required, because cutting off the constant engine ECU power supply also clears the learning values recorded in the engine ECU memory.
REFERENCE:
The hand-held tester communicates with the engine ECU, enabling it to do the following in addition to DTCoutput and clearing.
Check the freeze frame data.
Check the data monitored by the engine ECU.
Perform an active test that forces the actuators to drive

Diagnostic Mode Selection Function
The diagnostic system has two modes: Normal mode and check mode.
1. Normal mode
Use this mode for normal diagnosis.
2. Check mode
This mode provides higher diagnostic detection sensitivity than normal mode and makes it easier to detect malfunctions. It is easier to detect DTCs in this mode when performing malfunction reproduction tests on the vehicle. All DTCs and the freeze frame data will be cleared at this mode.
HINT:
There are two types for the check mode: By switching from normal mode when using a hand-held tester to communicate with the engine ECU, or by switching from normal mode when using TE1 and TE2 on the DLC.

The engine ECU possesses an OBD (On-Board Diagnostic) function which constantly monitors each sensor and actuator. If it detects a malfunction, the malfunction is recorded as a DTC (Diagnostic Trouble Code) and the MIL (Malfunction Indicator Lamp) on the combination meter lights up to inform the driver. By connecting the hand-held tester to DLC3, direct communication with the engine ECU can be performed via terminal SIL to confirm the DTC. The DTC can also be confirmed by causing the MIL to blink, then checking the blinking pattern.
HINT: The MIL may also be called the CHECK ENGINE warning light or engine system warning light.
Type of OBD
To confirm the DTC or data recorded by the engine ECU, a diagnosis system called MOBD, CARB OBD II, EURO OBD or ENHANCED OBD II is used to communicate directly with the engine ECU. Each of these systems displays a 5-digit DTC on the hand-held tester.
1. MOBD
The MOBD is diagnosis system unique to Toyota. It can be used to check the DTC or data for ToyotaÅfs own items.
2. CARB OBD II
The CARB OBD II is an emission diagnostic system used in the USA and Canada. It is used to check the DTC or data for items required by US and Canadian regulations.
3. EURO OBD
The EURO OBD is an emission diagnostic system used in Europe. It is used to check the DTC or data for items required by European regulations.
4. ENHANCED OBD II
The ENHANCED OBD II is a diagnostic system used in the USA and Canada. It is used to check items required by US and Canadian regulations, and check the DTC or data for ToyotaÅfs own items.
HINT: The earlier type of OBD used the MIL blinking pattern to check the DTC. The system read the data output by the engine ECU without communicating with the engine ECU.
Principal of Diagnosis
The engine ECU receives signals from the sensors in the form of voltage. The engine ECU can determine the conditions of the engine or the vehicle running by detecting the changes in the voltage of the signals that are output by the sensors. Thus, the engine ECU constantly monitors the input signals (voltage), compares them to the reference values that are stored in the engine ECU’s memory, and determines any abnormal conditions. The graph on the left shows the characteristics of a water temperature sensor. Normally, the voltage of the water temperature sensor should vary between 0.1V and 4.8V. When a voltage within this range is input, the engine ECU determines that the condition is normal. If short (the input voltage is less than 0.1 V) or broken wire (the input voltage is more than 4.8 V) occurs, it determines abnormal. However, even if the range of 0.1V to 4.8V is normal for diagnostic purposes, it may indicate a malfunction depending on the engine condition. The monitoring conditions of the DTC from the engine ECU differ according to the DTC, such as the requirement of driving, changes in the coolant temperature, etc., so refer to the Repair Manual for details
Function of MIL
The MIL has the following functions.
1. Lamp check function (engine stopped)
The MIL is turned on when the ignition switch is turned to ON, and it turns off when the engine speed reaches 400 rpm or more, to check whether the bulb is functioning or not.
2. Malfunction indicator function (engine running)
If the engine ECU detects a malfunction in a circuit, the engine ECU is monitoring while the engine is running, it turns on the MIL to inform the driver of a malfunction. When the malfunction has returned to normal, the lamp goes off after 5 seconds. For CARB OBD II and EURO OBD, when a malfunction returns to normal, the MIL turns off if no malfunction is detected in three continuous driving cycles.
HINT:
DTCs include some items where the DTC is stored in the engine ECU by detecting a malfunction, but the MIL does not turn on.
3. Diagnostic code display function
When shorted the terminals TE1-E1 on vehicles equipped with only DLC1 and DLC2, the DTC is displayed by the MIL blinking pattern. On vehicles equipped with DLC3, when shorted the terminals TC-CG, there are systems where the DTC is displayed by the MIL blinking pattern, and systems where the MIL does not blink.
1. MIL-ON one driving cycle detection
If a malfunction is detected during one driving cycle, the engine ECU turns the MIL on. The DTC and freeze frame data are simultaneously stored in the engine ECU when the MIL turns on.
HINT:
The freeze frame data is input/output signal data stored in the engine ECU when the DTC is detected.
2. MIL-ON two driving cycle detection
If the same malfunction is detected during two continuous driving cycle, the engine ECU turns the MIL on at two driving cycle. When the MIL turns on, the DTC and freeze frame data are simultaneously stored in the engine ECU. In this case, the malfunction that is detected at one driving cycle is stored as the pending code in the engine ECU. However the pending code is cleared if the same malfunction is not detected at two driving cycle. The function is activated when a malfunction occurs mainly in the emission system.
3. MIL blinking
If a misfire that may damage the catalytic converter is detected in the first driving cycle, the MIL blinks. If the same misfire is detected in the second driving cycle, the MIL blinks, and the DTC and freeze frame data are recorded in the engine ECU memory. If the misfire symptoms decline, the MIL changes from blinking to continuous illumination. *Driving cycle: One driving cycle refers to the period from when the engine is started until the engine is stopped.

The air intake control system is divided into two air cleaner inlets, and one of these inlets is provided with a valve, which is opened and closed to attain suitable air intake efficiency in accordance with the engine speed. This reduces the intake air noise in the low-speed range.
1. Construction
This system consists of the air intake control valve unit in the air cleaner inlet, the VSV (Vacuum Switching Valve) to control the vacuum which is the power source, and the check valve to prevent atmospheric air from flowing into the air intake chamber.
2. Operation
When the engine is running in the low- to mid-speed range, the engine ECU closes the air intake control valve. This causes an air intake on just one side, which reduces the air intake noise. When the engine is running in the high-speed range, the engine ECU opens the air intake control valve to allow air to be taken in from the two air inlets to improve the air intake efficiency.
Others
The following systems are also controlled by the engine ECU.
1. Fuel octane judgement
Depending on the model, the engine ECU determines the octane rating of the gasoline being used from the engine knocking signal of the knock sensor and then switches its internal ignition map to “premium” or “regular” to match the fuel being used.
2. ECT OD cut-off control system
To maintain good drivability and acceleration performance, the engine ECU sends an OD cut-off signal to the ECT ECU based on the signals from the water temperature sensor and vehicle speed sensor to prevent the automatic transmission from shifting into overdrive. In addition, in several engines the engine ECU sends the 3rd-gear cut-off signal to the ECT ECU.
3. EGR cut-off control system
This system shuts off the EGR (Exhaust Gas Recirculation) to maintain drivability when the engine is warming up, during high-speed driving, etc.
4. T-VIS (Toyota-Variable Induction System)
A valve is provided on one of the two intake manifolds of each cylinder to close the valve during low engine speeds and open the valve during high engine speeds. This improves engine performance in both the engine low- and high-speed ranges.
5. SCV (Swirl Control Valve) system
A valve is provided on one of the two intake ports of each cylinder to close the valve during low engine speeds and open the valve during high engine speeds in order to improve engine performance in both the engine lowand high-speed ranges. In addition, the other intake port has been given a shape so that its cross-sectional area is gradually decreased as it moves forward to increase the flow speed of the intake air passing through here. This causes the intake air to swirl in the cylinder increasing combustion efficiency and improving fuel efficiency in the low-speed range.
6. Turbocharging pressure control system
By controlling the boost pressure applied to the actuator for the waste gate valve, this system controls the air intake turbocharging pressure. This improves engine power while maintaining engine durability thus improving drivability.
7. Supercharger control system
This system controls everything related to the supercharger, such as starting and stopping the supercharger, and opening and closing the air bypass when the supercharger is stopped.
8. EHPS (Electro-Hydraulic Power Steering) control system
This control is only provided in vehicles with an EHPS that uses an electric motor to drive the vane pump. This system controls the vane pump motor speed. For example, the vane pump is stopped to ensure the startability or prevent the engine from stalling when the engine is cold or the engine speed is extremely low.

The evaporative emission control system prevents evaporated fuel from the fuel tank from being released into the atmosphere by having the evaporative emissions be temporarily absorbed by a charcoal canister. These emissions are later taken in and combusted after the engine warms up.
Construction
The evaporative emission control system has passages and valves among the air cleaner, intake manifold, charcoal canister, and fuel tank as shown in the illustration. These are used to open and close the VSV, etc., to allow the engine ECU to control the movement of evaporated fuel for the entire system.
REFERENCE
Monitoring
The monitoring sequence is conducted when the air temperature sensor and the water temperature sensor show nearly the same values, such as during cold engine startup. The engine ECU uses the vapor pressure sensor to continuously monitor the fuel tank pressure, and when a malfunction is detected in the pressure, a DTC (Diagnosis Trouble Code) is stored in memory and the malfunction indicator lamp is turned ON to warn the driver. The engine ECU closes the canister closed valve and opens the purge valve and pressure switching valve to apply a vacuum to the entire system. When sufficient vacuum is applied, the engine ECU closes the purge valve to close the passages throughout the system. After this, the engine ECU conducts monitoring to check for leaks as the system pressure is gradually increased to a set vacuum. The engine ECU then operates the valves in the order of canister closed valve and then pressure switching valve, and then determines as the pressure changes whether or not the VSVs are good.
Operations
Purge flow
When the engine reaches certain conditions, the engine ECU opens the VSV (for canister closed valve) while controlling the VSV (for EVAP) using duty ratio control. This causes the intake manifold vacuum to open the air inlet valve and allow the gas absorbed by the canister to be taken together with air from the air cleaner via the VSV (for canister closed valve) into the intake manifold. The engine ECU uses duty ratio control for the VSV (for EVAP) to prevent an excessive purge flow during idling and other conditions, engine failure, and emissions from worsening.

The AI control system/AS control system is a system that feeds air into the exhaust manifold to recombust the uncombusted gas in the exhaust to lower HC and CO emissions. The difference between these two systems is that the AI control system uses a pump to force feed the air while the AS control system uses the vacuum created in the exhaust manifold to draw in air. The AI control system will be explained here. This system is operated by the engine ECU when HC and CO exhaust emissions increase when the engine is cold and the vehicle is decelerating. This system is not used under any other conditions. When all of the operation conditions exist, the engine ECU operates the electric air pump while the VSV operates at the same time to feed the intake manifold vacuum to the air injection valve. This opens the passage to feed the compressed air to the exhaust manifold. The engine ECU estimates the total volume of gas flowing in the TWC based on the signal from the air flow meter.
REFERENCE:
Past AI control systems kept the air pump operating at all times. Therefore, an ASV (Air Switching Valve) was used instead of an air injection valve to expel the compressed air when the system was not in operation.

The ACIS (Acoustic Control Induction System) changes the effective length of the intake manifold to increase power over a wide range from low speed to high speed. This system uses an intake air control valve to divide the intake manifold into two stages that make it possible to change the effective length of the intake manifold to match the engine speed and throttle valve opening. There are several types of ACIS. The example used here is that for the 3UZ-FE engine.
1. Construction
The main components of the system are described below.
(1) Intake air control valve
The intake air control valve is in the intake air chamber, and is opened and closed to change the effective length of the intake manifold in two stages.
(2) VSV (Vacuum Switching Valve)
According to the ACIS signal from the engine ECU, the VSV control the vacuum, which is the power source for operating the actuator of intake air control valve.
(3) Vacuum tank
The vacuum tank has a built-in check valve. And it stores the vacuum applied to the actuator so that the intake air control valve can be fully closed even in the low-vacuum condition.

2. Operation
(1) When the air intake control valve closes (VSV ON)
When the engine ECU turns ON the VSV to match the long pulsation cycle, a vacuum is applied to the actuator diaphragm chamber. This closes the control valve. This in turn, lengthens the effective length of the intake manifold, which improves the air intake effect and power in the low- and medium-speed ranges due to the intake air pulsation effect.
(2) When the air intake control valve open (VSV OFF)
When the engine ECU turns OFF the VSV to match the short pulsation cycle, atmospheric pressure is applied to the actuator diaphragm chamber, opening the control valve. When the control valve opens, the effective length of the intake manifold is shortened, which provides maximum air intake effectiveness to increase power in the high-speed range.

The detection capability of the oxygen sensor and A/F (air-fuel) ratio sensor decline at low temperatures (under 400 °C). Therefore, some oxygen sensor or A/F ratio sensor are provided with a heater to heat the elements. The engine ECU controls the amount of the current of the heater in accordance with the intake air mass and engine speed. In other words, when the engine load is small and the exhaust gas temperature is low, the amount of the current flowing to the heater increases in order to maintain the sensor efficiency. However, when the engine load and exhaust gas temperature increase, the heater is stopped operating or the amount of the current flowing to the heater is decreased.
Air Conditioner Control System
The engine ECU turns OFF the A/C compressor in accordance with vehicle conditions to maintain good drivability and acceleration performance. For example, when rapidly accelerating from a low engine speed, the engine ECU turns OFF the A/C compressor in accordance with the vehicle speed, engine speed, throttle valve position, and intake manifold pressure or intake air mass. There are two types of air conditioner control systems. One type indirectly controls the air conditioner operation via the A/C amplifier. The engine ECU sends an ACT signal to the A/C amplifier to disengage the magnetic clutch of the A/C compressor. In the other type, the engine ECU directly controls the air conditioner operation by operating the magnetic clutch relay. With some engine models, after the air conditioner switch is turned ON, the magnetic clutch operation is delayed for a moment. At this time, the engine ECU opens the ISC valve to increase the engine speed to prevent the engine speed from dropping when the air compressor operates. This delay control function is called air conditioner compressor delay control.
Cooling Fan Control
There are various types of cooling fan controls in addition to the one shown in the illustration. Up to now, the fan speed was controlled by having the water temperature switch control the fan relay. Currently, some engine ECUs control the fan relay to control the fan speed, or the cooling fan ECU to control the fan speed.
HINT:
As shown in the illustration, low speed operation lowers the voltage applied to the motor using a resistor placed in series in the circuit to reduce the cooling fan speed, or two motors are connected in series to reduce the fan speed.