Engine Control System (Diagnostic Codes & Circuit Tests) (2ZR-FAE): Overview Toyota Corolla XI

DESCRIPTION

Refer to DTC P2120.

Refer to DESCRIPTION

MONITOR DESCRIPTION

The accelerator pedal position sensor is mounted on the accelerator pedal bracket. The accelerator pedal position sensor has 2 sensor elements and 2 signal outputs: VPA and VPA2. VPA is used to detect the actual accelerator pedal angle (used for engine control) and VPA2 is used to detect malfunctions in VPA. When the difference between the output voltages of VPA and VPA2 deviates from the standard, the ECM determines that the accelerator pedal position sensor is malfunctioning. The ECM illuminates the MIL and stores this 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 time. 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 a 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), current flows to 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 alumina, and therefore the 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 88

HINT

1. When any of these DTCs is 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 output voltage cannot be confirmed without using the Techstream.
4. If an air fuel ratio sensor malfunction is detected, the ECM will store 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 0.66 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 89

Refer to DTC P0300.

Refer to DESCRIPTION

Refer to DTC P2195.

Refer to DESCRIPTION

Fuel System Air Fuel Ratio Cylinder Imbalance Monitor

The ECM uses the air fuel ratio sensor and crankshaft position sensor to monitor the difference in air fuel ratios between the cylinders caused by differences in injection volumes 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 air fuel ratios between the cylinders due to fluctuation in the air fuel ratio sensor output over 1 engine cycle (2 crankshaft revolutions), the system determines that there is a problem.

Crankshaft Position Sensor Monitoring Method: 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 air fuel ratios between the cylinders, which it determines to be a problem.

Refer to DTC P2195.

Refer to DESCRIPTION

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, 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 between 0.5 V and 4.5 V, 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 the next driving cycle, the ECM will illuminate the MIL and store a DTC.

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 90

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. In this case the ECM will illuminate the MIL and store this DTC.

Scheme 91

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 92

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 this DTC the next time the ignition switch is turned to ON.

The EDU in the continuously variable valve lift controller assembly sends a motor drive request and supplies current to the motor.

Perform the following procedure to confirm that the VALVEMATIC system is operating normally.

1. Connect the Techstream to the DLC3.
2. Start the engine.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VALVEMATIC(ENG ON) / Gas Valve Control / VALVEMATIC Current Angle and VALVEMATIC Target Angle. NOTE: Make sure the following conditions are met when performing the Active Test. The engine is running. The engine coolant temperature is 40°C (104°F) or higher. The vehicle is stationary. The shift lever is in P or N. Result The "VALVEMATIC Current Angle" follows the "VALVEMATIC Target Angle".

HINT

If the malfunction does not recur, refer to the engine coolant temperature and intake air temperature recorded in the freeze frame data and perform a simulation test.

When the Active Test results are abnormal, remove the continuously variable valve lift controller assembly from the camshaft housing sub-assembly and perform the "Activate the VALVEMATIC(ENG OFF)" Active Test with the removed continuously variable valve lift controller assembly to determine whether the problem is with the continuously variable valve lift controller assembly or camshaft housing sub-assembly.

When the EDU in the continuously variable valve lift controller assembly detects that the actuator does not operate even though the EDU commands the actuator to operate and power is supplied to the actuator, a DTC is stored and the MIL is illuminated.

The current flowing to the actuator in the continuously variable valve lift controller assembly is monitored by the current sensor in the continuously variable valve lift controller assembly.

When the continuously variable valve lift controller assembly detects that no current is flowing to the actuator even though the actuator is commanded to operate or the current flowing to the actuator is more than the amount requested, a DTC is stored and the MIL is illuminated.

There are position sensor and angle sensor in the continuously variable valve lift controller assembly. They detect the actuator position and rotation direction.

There are position sensor and angle sensor in the continuously variable valve lift controller assembly. When there is a malfunction in any of the sensors, this DTC is stored and the MIL is illuminated.

The VALVEMATIC shaft sensor (No. 1 crank position sensor) detects the position of the shaft monitor target mounted on the VALVEMATIC control shaft and the ECM detects the operation of the VALVEMATIC control shaft.

If the duration monitored by the continuously variable valve lift controller assembly differs from the VALVEMATIC shaft sensor (No. 1 crank position sensor) output, or the VALVEMATIC shaft sensor (No. 1 crank position sensor) voltage is less than 0.38 V or higher than 4.68 V for 5 seconds or more, the ECM illumiates the MIL and stores a DTC.

The ECM and continuously variable valve lift controller assembly communicate via the CAN communication system.

When between the ECM and the continuously variable valve lift controller assembly is a malfunction in the CAN communication, this DTC is stored and the MIL is illuminated.

The VALVEMATIC system is able to continuously change the valve lift amount and valve timing. For engines equipped with a VALVEMATIC system, when a part such as a rocker arm in the camshaft housing has mechanical problems, the valve lift amount does not change and problems occur, such as a lack of engine power or rough idling.

When the ignition switch is turned to ON, the battery voltage is applied to IGSW of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil, closing the contacts of the EFI-MAIN relay and supplying power to terminal is +B and +B2 of the ECM.

Scheme 93

The ECM constantly generates a 5 V power source voltage from the 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 94

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. The MIL goes off when the engine is started.

Scheme 95

Scheme 96

The fuel pump circuit consists of the ECM, fuel pump and fuel pump control ECU assembly (which operates the fuel pump). Based on the engine output, the ECM determines the fuel pump speed. The speed is then converted to a duty signal and sent to the fuel pump control ECU assembly. Based on the signal sent from the ECM, the fuel pump ECU adjusts the fuel pump operation speed.

Scheme 97

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

Scheme 98

While the engine is being cranked, current flows from terminal ST2 of the ignition switch assembly*1 or terminal STAR of the certification ECU (smart key ECU assembly)*2 to the park/neutral position switch assembly and to terminal STA of the ECM (STA signal).

*1: w/o smart key system

*2: w/ smart key system

When the vehicle is being driven, depressing the accelerator pedal sensor assembly and brake pedal will activate the brake override system to restrict driving torque. The conditions for activating the brake override system as well as the items that are controlled are explained below.

Scheme 99

Activation Conditions

1. Vehicle is running at or above the specified speed.
2. When the accelerator pedal and brake pedal are depressed.

Note. The vehicle may not enter the brake override system control due to the relation of the accelerator pedal angle and the vehicle's speed.

Items Controlled

1. Driving torque is restricted.

HINT

When this control is activated, the accelerator opening value is forcibly reduced to a fixed value. Therefore, the Accelerator Position value in the Data List is fixed regardless of the actual accelerator opening value (Accel Sens. No. 1 Volt %).

Deactivation Conditions

1. When the brake pedal or the accelerator pedal returns to some degree.

The MIL (Malfunction Indicator Lamp) is used to indicate vehicle malfunctions detected by the ECM. When the ignition switch is turned to ON, 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, the MIL should be illuminated and should turn off after engine is started. If the MIL remains illuminated or is not illuminated, conduct the following troubleshooting procedure using the Techstream.

Scheme 100

See also:
• ON-VEHICLE INSPECTION [08/2013 - ]
• PROCEDURE - Step 2
• PROCEDURE - Step 3
• REMOVAL [08/2013 - ]