Engine Control System (1NZ-FXE) (Diagnostic Codes & Circuit Tests): Overview Toyota Prius C I facelift

DESCRIPTION

When the engine is idling stably under a low load, if the idle speed drops or becomes unstable, this DTC will be stored.

Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

The throttle actuator is operated by the ECM and opens and closes the throttle valve using gears.

The opening angle of the throttle valve is detected by the throttle position sensor, which is mounted on the throttle body with motor assembly. The throttle position sensor provides feedback to the ECM. This feedback allows the ECM to appropriately control the throttle actuator and monitor the throttle opening angle as the ECM responds to driver inputs.

HINT

This Electronic Throttle Control System (ETCS) does not use a throttle cable.

MONITOR DESCRIPTION

The ECM monitors the electrical current through the electronic actuator, and detects malfunctions and open circuits in the throttle actuator based on this value. If the current is outside the standard range, the ECM determines that there is a malfunction in the throttle actuator. In addition, if the throttle valve does not function properly (for example, stuck on), the ECM determines that there is a malfunction. The ECM then illuminates the MIL and stores a DTC.

The idle speed is controlled by the Electronic Throttle Control System (ETCS). The ETCS is comprised of a throttle actuator, which operates the throttle valve, and a throttle position sensor, which detects the opening amount of the throttle valve. The ECM controls the throttle actuator to adjust the throttle valve opening amount so that the idle speed is maintained at the target idle speed.

HINT

1. The ISC learned value is the calculated intake air amount corresponding to the throttle opening amount necessary to maintain the idle speed.
2. This malfunction is only detected once per trip. After it has been detected once, the system will not monitor for the malfunction for the rest of the trip.
3. The system uses the throttle body with motor assembly and mass air flow meter sub-assembly to detect this malfunction.

If there are deposits in the throttle valve, a decrease in the ISC flow rate may cause engine stall or unstable idling. Therefore, the necessary ISC flow rate for idling is maintained using the ISC learned value and feedback. The ECM stores this DTC if the ISC learned value approaches its limit. The ECM begins monitoring for the DTC detection conditions when the following preconditions are met

1. 1) The mass air flow meter sub-assembly is normal.
2. 2) Atmospheric pressure is 85 kPa(abs) [638 mmHg(abs)] or higher.
3. 3) The vehicle has been driven at a speed of 30 km/h (18.6 mph) or more at least once.
4. 4) The engine coolant temperature is 45°C (113°F) or less at engine start, the engine is warmed up and conditions for ISC learning are met, or the ignition switch has been turned to ON (IG) (include engine running) for 1 hour or more, the engine is warmed up and conditions for ISC learning are met.

The throttle actuator is operated by the ECM, and opens and closes the throttle valve using gears. The opening angle of the throttle valve is detected by the throttle position sensor, which is mounted on the throttle body with motor assembly. The throttle position sensor provides feedback to the ECM. This feedback allows the ECM to appropriately control the throttle actuator and monitor the throttle opening angle as the ECM responds to driver inputs.

HINT

This Electronic Throttle Control System (ETCS) does not use a throttle cable.

The ECM determines that there is a malfunction in the ETCS when the throttle valve remains at a fixed angle despite a high drive current from the ECM. The ECM illuminates the MIL and stores a DTC.

The electronic throttle control system has a dedicated power supply circuit. The voltage (+BM) is monitored and when it is low (below 4 V), the ECM determines that there is a malfunction in the electronic throttle control system and cuts off the current to the throttle actuator.

When the voltage becomes unstable, the electronic throttle control system itself becomes unstable. For this reason, when the voltage is low, the current to the throttle actuator is cut. If repairs are made and the system returns to normal, turn the ignition switch off. The ECM then allows the current to flow to the throttle actuator so that it can be restarted.

HINT

The electronic throttle control system does not use a throttle cable.

Scheme 42

The ECM monitors the auxiliary battery supply voltage applied to the throttle actuator.

When the power supply voltage (+BM) is less than 4 V for 0.8 seconds or more, the ECM interprets this as an open in the power supply circuit (+BM). The ECM illuminates the MIL and stores the DTC.

The electronic throttle control system is composed of the throttle actuator, throttle position sensor, accelerator pedal position sensor, and ECM. The ECM operates the throttle actuator to regulate the throttle valve in response to driver inputs. The throttle position sensor detects the opening angle of the throttle valve, and provides the ECM with feedback so that the throttle valve can be appropriately controlled by the ECM.

The ECM determines the actual opening angle of the throttle valve from the throttle position sensor signal. The actual opening angle is compared to the target opening angle commanded by the ECM. If the difference between these two values is outside the standard range, the ECM interprets this as a malfunction in the electronic throttle control system. The ECM then illuminates the MIL and stores the DTC.

HINT

Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.

The air fuel ratio sensor generates a voltage* that corresponds to the actual air fuel ratio. This sensor voltage is used to provide the ECM with feedback so that it can control the air fuel ratio. The ECM determines the deviation from the stoichiometric air fuel ratio level, and regulates the fuel injection duration. If the air fuel ratio sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.

The air fuel ratio sensor is a planar type and is integrated with the heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are a narrow type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, and therefore sensor activation is accelerated.

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a three-way catalytic converter is used. For the most efficient use of the three-way catalytic converter, the air fuel ratio must be precisely controlled so that it is always close to the stoichiometric level.

*: Value changes inside the ECM. Since the air fuel ratio sensor is a current output element, the current is converted into a voltage inside the ECM. Any measurements taken at the air fuel ratio sensor or ECM connectors will show a constant voltage.

Scheme 43

HINT

1. When any of these DTCs are stored, check the air fuel ratio sensor voltage output by entering the following menus on the Techstream: Powertrain / Engine and ECT / Data List / Gas AF Control / AFS Voltage B1S1.
2. Short-term fuel trim values can also be read using the Techstream.
3. The ECM regulates the voltages at the A1A+ and A1A- terminals of the ECM to a constant level. Therefore, the air fuel ratio sensor voltage output cannot be confirmed without using the Techstream.
4. If an air fuel ratio sensor malfunction is detected, the ECM stores a DTC.

Sensor Voltage Detection Monitor

Under air fuel ratio feedback control, If the air fuel ratio sensor output voltage is less than 2.8 V (very rich condition) for 5 seconds despite the heated oxygen sensor output voltage being less than 0.69 V, the ECM stores DTC P2196. Alternatively, if the air fuel ratio sensor output voltage is higher than 3.8 V (very lean condition) for 5 seconds despite the heated oxygen sensor output voltage being 0.21 V or higher, DTC P2195 is stored.

Sensor Current Detection Monitor

A rich air fuel mixture causes a low air fuel ratio sensor current, and a lean air fuel mixture causes a high air fuel ratio sensor current. Therefore, the sensor output becomes low during acceleration, and it becomes high during deceleration with the throttle valve fully closed. The ECM monitors the air fuel ratio sensor current during fuel-cut and detects any abnormal current values.

If the air fuel ratio sensor output is 2.2 mA or higher for more than 3 seconds of cumulative time, the ECM interprets this as a malfunction in the air fuel ratio sensor and stores DTC P2195 (stuck on high side). If the air fuel ratio sensor output is less than 0.7 mA for more than 3 seconds of cumulative time, the ECM stores DTC P2196 (stuck on low side).

Scheme 44

Refer to P0300. Refer to DESCRIPTION.

Refer to P2195. Refer to DESCRIPTION.

Fuel System Air Fuel Ratio Cylinder Imbalance Monitor

The ECM uses the air fuel ratio sensor and crank position sensor to monitor the difference in air fuel ratio between the cylinders caused by differences in injection volume between the cylinders, leakage in the intake or exhaust system, etc.

When the air fuel ratios of the cylinders are lean or rich with respect to each other, the ECM determines that a problem is present and stores a DTC.

Air Fuel Ratio Sensor Monitoring Method: P219A is stored primarily when a rich side imbalance is detected.

When the system detects a difference in the air fuel ratio between the cylinders due to fluctuation of the air fuel ratio sensor output over 1 engine cycle (2 crankshaft revolutions), the system determines that there is a problem.

Crank Position Sensor Monitoring Method: P219A, P219C, P219D, P219E and/or P219F are stored primarily when a lean side imbalance is detected.

The system monitors the engine speed variation and when the variation becomes large, the system determines that there is a difference in the air fuel ratio between the cylinders, which it determines to be a problem.

HINT

1. Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.
2. Refer to DTC P2195. Refer to «DESCRIPTION»(ref-651307-S28809102042014081900000).

These DTCs are output when there is an open or short in the air fuel ratio sensor circuit, or if the air fuel ratio sensor output drops. To detect these problems, the voltage of the air fuel ratio sensor is monitored when turning the ignition switch to ON (IG), and the admittance (admittance is an electrical term that indicates the ease of flow of current) is checked while driving. If the voltage of the air fuel ratio sensor is higher than 0.5 V, and 4.5 V or less it is considered normal. If the voltage is out of the specified range, or the admittance is less than the standard value, the ECM determines that there is a malfunction in the air fuel ratio sensor. If the same malfunction is detected in next driving cycle, the MIL is illuminated and a DTC is stored.

The description can be found in EVAP (Evaporative Emission) System. Refer to DESCRIPTION.

5 hours* after the ignition switch is turned off, the leak detection pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure.

HINT

*: If the engine coolant temperature is not less than 35°C (95°F) 5 hours after the ignition switch is turned off, the monitor check starts 2 hours later. If it is still not less than 35°C (95°F) 7 hours after the ignition switch is turned off, the monitor check starts 2.5 hours later.

*: If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.

Scheme 45

TEXT IN ILLUSTRATION

P2420: Vent valve stuck open (vent)

In operation C, the vent valve turns on (closed) and the EVAP system pressure is then measured by the ECM using the canister pressure sensor to conduct an EVAP leak check. If the pressure does not increase when the vent valve is open, the ECM interprets this as the vent valve being stuck open. The ECM illuminates the MIL and stores the DTC.

Scheme 46

The soak timer operates after the ignition switch is turned off. When a certain amount of time has elapsed after turning the ignition switch off, the soak timer activates the ECM to perform malfunction checks which can only be performed after the engine is stopped. The soak timer is built into the ECM.

Scheme 47

If the soak timer activates the ECM even though only a short amount of time has elapsed since the ignition switch was turned off, or if the soak timer does not activate the ECM even though a considerable amount of time has elapsed since the ignition switch was turned off, the ECM determines that the soak timer is malfunctioning, illuminates the MIL and stores a DTC the next time the ignition switch is turned to ON (IG).

The ECM controls the engine water pump assembly by calculating the necessary amount of coolant flow based on engine coolant temperature, engine speed and vehicle speed information. The speed of the engine water pump assembly is controlled steplessly using a duty cycle signal sent from the ECM. This optimal control enhances warm-up performance and reduces cooling losses, thus reducing the specific fuel consumption of the engine.

The ECM calculates the speed of the engine water pump assembly using a duty cycle signal sent from the engine water pump assembly. When the speed of the engine water pump assembly becomes less than 900 RPM while it is operating, the ECM detects the malfunction and stores DTC P261B.

The engine water pump assembly operates steplessly based on a duty cycle signal sent from the ECM. If actual drive duty cycle ratio does not correspond to the target drive duty cycle of the engine water pump assembly, the ECM detects the malfunction.

The ECM receives signals from the power management control ECU such as the requested engine torque, target engine speed and engine cranking status, and controls the engine output based on the target engine speed and requested torque.

1. The ECM receives signals such as requested engine torque, target engine speed and engine cranking status from the power management control ECU.
2. The ECM controls engine start and stop and the throttle valve angle based on the signals received from the power management control ECU.
3. The ECM receives the actual engine torque calculated by the power management control ECU based on the generator torque.
4. When the actual engine torque is less than 20% of the requested engine torque*1, the ECM judges that the engine output is abnormal and stores DTC P3190. (The engine may not have started in the above situation.) *1: Requested torque = Requested Engine Torque (kW) / HV Target Engine Speed (RPM) x 9549
5. If the ECM does not detect engine start torque (actual engine torque) even though it has received an engine start request and started the engine, it stores DTC P3191. HINT: When DTC P3190, P3191 or P3193 is stored, engine operation is disabled. In this case, add fuel or perform a repair, then clear the DTCs and turn the ignition switch off to allow the operation to return to normal. When DTC P3190, P3191 or P3193 is stored, the HV battery is not charged as the vehicle operates using only the motor. If the vehicle is driven in this condition, the SOC will drop and the HV battery will be depleted, preventing the system from entering the READY-on state. When DTC P3190 or P3191 is stored, the engine torque has dropped by 80% or the engine cannot be started. If any DTCs that indicate malfunctioning of engine related parts are stored at the same time, repair the malfunctioning parts first.

RELEVANT DATA LIST ITEMS

The ECM receives the fuel low level signal from the combination meter sub-assembly (meter ECU) to detect if the vehicle is running out of fuel.

This DTC indicates that the vehicle ran out of fuel. If the ECM receives the fuel low level signal from the combination meter sub-assembly (meter ECU) and the DTC detection conditions of either DTC P3190 or P3191 are met while the ignition switch is ON (IG) or the engine is operating, the ECM stores this DTC.

The Controller Area Network (CAN) is a serial data communication system for real-time application. It is a multiplex communication system designed for on-vehicle use that provides a superior communication speed of 500 kbps and a capability to detect malfunctions. Through the combination of the CANH and CANL bus lines, the CAN is able to maintain communication based on differential voltage.

When the ignition switch is turned to ON (IG), auxiliary battery voltage is applied to the IGSW terminal of the ECM. The output signal from the MREL terminal of the ECM causes current to flow to the coil of the No. 1 integration relay (EFI MAIN relay), closing the contact and supplying power to terminals +B and +B2 of the ECM.

Scheme 48

The ECM constantly generates a 5 V power source voltage from the auxiliary battery voltage supplied to the +B (BATT) terminal to operate the microprocessor. The ECM also provides this power source voltage to the sensors through the VC output circuit.

Scheme 49

When the VC circuit is short-circuited, the microprocessor in the ECM and the sensors that are supplied with power through the VC circuit are inactivated because power is not supplied from the VC circuit. Under this condition, the system does not start up and the MIL does not illuminate even if the system malfunctions.

HINT

Under normal conditions, the MIL is illuminated when the ignition switch is turned to ON (IG). The MIL goes off when the ignition switch ON (READY).

Scheme 50

When the engine is cranked, the start request signal output from the power management control ECU *1, or ignition or starter switch assembly*2 is input to the ECM, and the NE signal generated by the crank position sensor is also input to the NE+ terminal. Thus, the ECM interprets that the engine has been cranked, and turns transistor Tr1 in the ECM internal circuit on. Current flows to the C/OPN (Circuit Opening) relay by turning Tr1 on. Then, the fuel pump with filter assembly operates.

While the NE signal is input to the ECM with the engine running, the ECM turns Tr1 on continuously.

1. *1: w/ Smart Key System
2. *2: w/o Smart Key System

Scheme 51

The fuel injectors are located on the intake port. They inject fuel into the cylinders based on the signals from the ECM.

Scheme 52

Scheme 53

The MIL (Malfunction Indicator Lamp) is used to indicate vehicle malfunctions detected by the ECM. When the ignition switch is turned to ON (IG), power is supplied to the MIL circuit, and the ECM provides the circuit ground which illuminates the MIL.

The MIL operation can be checked visually: When the ignition switch is turned to ON (IG), the MIL should be illuminated and should turn off after ignition switch ON (READY). If the MIL remains illuminated or is not illuminated, conduct the following troubleshooting procedure using the Techstream.

Scheme 54

Scheme 55

See also:
• ON-VEHICLE INSPECTION [12/2013 - ]
• ON-VEHICLE INSPECTION [12/2013 - ] - Step 2
• ON-VEHICLE INSPECTION [12/2013 - ] - Step 3
• REMOVAL [12/2013 - ]