Engine Control System (Diagnostic Codes (P1603 - P2195)): Overview Lexus RX III рестайлинг

DESCRIPTION

P1603

After starting the engine, this DTC is stored when the engine stops without the engine switch being operated.

Using the Techstream, the conditions present when the DTC was stored can be confirmed by referring to the freeze frame data. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.

It is necessary to check if the vehicle has ran out of fuel before performing troubleshooting, as this DTC is also stored when the engine stalls due to running out of fuel.

P1605

This DTC is stored if the engine speed drops below the set speed.

Using the Techstream, the conditions present when the DTC was stored can be confirmed by referring to the freeze frame data. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.

It is necessary to check if the vehicle ran out of fuel before performing troubleshooting, as this DTC is also stored when idling is unstable due to running out of fuel.

Scheme 174

Scheme 175

1. Reference waveforms showing a normal cold engine start
2. Reference waveforms showing a normal warm engine start
3. Reference values when there is an air leak in the intake system during rough idling FREEZE FRAME DATA P1605 ROUGH IDLING Parameter -3 -2 -1 0 1 Unit Engine Speed 647 649 586 378 182 RPM Calculate Load 26.2 26.2 29.1 42.6 58.6 % Vehicle Load 11.7 11.7 12.1 48.7 61.2 % MAF 2.87 2.87 2.87 6.23 3.04 gm/s Atmosphere Pressure -0 -0 -0 -0 -0 kPa Coolant Temp 187 187 187 187 187 F Intake Air 109 109 109 109 109 F Battery Voltage 13.515 13.515 13.264 12.892 12.792 V Throttle Sensor Volt % 14.5 14.5 14.5 16.8 17.2 % Throttle Sensor #2 Volt % 46.2 46.2 46.2 48.4 49.2 % Throttle Sensor Position 0.0 0.0 0.0 0.0 0.0 % Throttle Motor DUTY 14.5 14.5 14.5 17.2 17.2 % Injector (Port) 2159 2161 2148 2190 2190 μs Injection Volume (Cylinder 1) 0.093 0.093 0.093 0.095 0.095 ml Fuel Pump Duty 58.6 58.6 58.6 58.6 58.6 % EVAP (Purge) VSV 13.3 13.3 13.3 13.3 13.3 % Evap Purge Flow 2.9 2.9 2.9 3.2 3.2 % Purge Density Learn Value 0.891 0.891 0.891 0.891 0.891 EVAP System Vent Valve OFF OFF OFF OFF OFF EVAP purge VSV OFF OFF OFF OFF OFF Purge Cut VSV Duty 8.5 8.5 8.5 8.5 8.5 % Target Air-Fuel Ratio 0.998 0.998 0.998 0.998 0.998 AF Lambda B1S1 0.999 0.997 1.001 1.038 1.118 AF Lambda B2S1 0.997 0.994 0.999 1.036 1.112 AFS Voltage B1S1 3.258 3.242 3.284 3.521 3.715 V AFS Voltage B2S1 3.251 3.306 3.324 3.497 3.689 V O2S B1S2 0.740 0.740 0.740 0.740 0.740 V O2S B2S2 0.760 0.760 0.760 0.760 0.760 V Short FT #1 -1.563 -1.563 -1.563 -1.563 -1.563 % Long FT #1 6.250 6.250 6.250 6.250 6.250 % Total FT #1 0.054 0.054 0.054 0.054 0.054 Sort FT #2 -0.782 -0.782 -0.782 -0.782 -0.782 % Long FT #2 7.031 7.031 7.031 7.031 7.031 % Total FT #2 0.062 0.062 0.062 0.062 0.062 Fuel System Status #1 CL CL CL CL CL Fuel System Status #2 CL CL CL CL CL IGN Advance 22.0 22.0 22.5 23.5 23.5 deg Knock Feedback Value -1.5 -1.5 -1.5 -1.5 -1.5 deg(CA) Knock Correct Learn Value 17.0 17.0 17.0 17.0 17.0 deg(CA) Starter Signal Close Close Close Close Close

This DTC is stored when the engine does not start even though the STA signal is input or when the engine takes a long time to start, and when the engine speed is low or the engine stalls just after the engine starts.

Using the Techstream, the conditions present when the DTC was stored can be confirmed by referring to the freeze frame data. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.

It is necessary to check if the vehicle ran out of fuel before performing troubleshooting, as this DTC is also stored when there is engine starting trouble due to running out of fuel.

Scheme 176

1. Reference waveforms showing a normal cold engine start
2. Reference waveforms showing a normal warm engine start
3. Reference values when there is an air leak in the intake system during starting difficulty FREEZE FRAME DATA P1604 STARTABILITY MALFUNCTION Parameter -3 -2 -1 0 1 Unit Engine Speed 1489 986 345 186 124 RPM Calculate Load 36.2 28.2 31.4 92.4 94.6 % Vehicle Load 7.9 7.9 9.2 7.2 6.0 % MAF 10.12 5.04 2.79 0.81 0.68 gm/sec Atmosphere Pressure -0 -0 -0 -0 -0 kPa Coolant Temp 185 185 185 185 185 F Intake Air 102 102 102 102 102 F Battery Voltage 13.222 13.300 12.109 11.972 11.854 V Throttle Sensor Volt % 16.5 16.5 16.0 15.6 15.6 % Throttl Sensor #2 Volt % 48.2 48.2 47.8 47.2 47.2 % Throttle Sensor Position 0.0 0.0 0.0 0.0 0.0 % Throttle Motor DUTY 16.5 16.5 16.0 15.6 15.6 % Injector (Port) 3628 2620 2744 2744 2744 μs Injection Volume (Cylinder 1) 3.062 0.226 0.226 0.226 0.226 ml Fuel Pump Duty 58.6 58.6 58.6 58.6 58.6 % EVAP (Purge) VSV 0.0 0.0 0.0 0.0 0.0 % Evap Purge Flow 0.0 0.0 0.0 0.0 0.0 % Purge Density Learn Value 0.000 0.000 0.000 0.000 0.000 EVAP System Vent Valve OFF OFF OFF OFF OFF EVAP purge VSV OFF OFF OFF OFF OFF Purge Cut VSV Duty 0.0 0.0 0.0 0.0 0.0 % Target Air-Fuel Ratio 0.998 0.998 0.998 0.998 0.998 AF Lambda B1S1 0.999 0.999 0.999 0.999 0.999 AF Lambda B2S1 0.997 0.997 0.997 0.998 0.998 AFS Voltage B1S1 3.258 3.258 3.258 3.258 3.258 V AFS Voltage B2S1 3.251 3.251 3.251 3.253 3.253 V O2S B1S2 0.000 0.000 0.000 0.000 0.000 V O2S B2S2 0.015 0.015 0.015 0.000 0.000 V Short FT #1 0.000 0.000 0.000 0.000 0.000 % Long FT #1 8.782 4.354 -2.665 -2.665 -2.665 % Total FT #1 0.058 0.058 0.058 0.058 0.058 Sort FT #2 0.000 0.000 0.000 0.000 0.000 % Long FT #2 9.264 4.587 -2.462 -2.462 -2.462 % Total FT #2 0.062 0.062 0.062 0.062 0.062 Fuel System Status #1 OL OL OL OL OL Fuel System Status #2 OL OL OL OL OL IGN Advance 0.0 10.5 16.5 18.0 18.0 deg Knock Feedback Value -1.5 -1.5 -1.5 -1.5 -1.5 CA Knock Correct Learn Value 17.0 17.0 17.0 17.0 17.0 CA Starter Signal Close Close Close Close Close

This DTC is stored when the engine does not start even though the STA signal is input or when the engine takes a long time to start, and when the engine speed is low or the engine stalls just after the engine starts.

Using the Techstream, the conditions present when the DTC was stored can be confirmed by referring to the freeze frame data. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.

It is necessary to check if the vehicle ran out of fuel before performing troubleshooting, as this DTC is also stored when there is engine starting trouble due to running out of fuel.

1. Reference waveforms showing a normal cold engine start
2. Reference waveforms showing a normal warm engine start
3. Reference values when there is an air leak in the intake system during starting difficulty FREEZE FRAME DATA P1604 STARTABILITY MALFUNCTION Parameter -3 -2 -1 0 1 Unit Engine Speed 1489 986 345 186 124 RPM Calculate Load 36.2 28.2 31.4 92.4 94.6 % Vehicle Load 7.9 7.9 9.2 7.2 6.0 % MAF 10.12 5.04 2.79 0.81 0.68 gm/s Atmosphere Pressure -0 -0 -0 -0 -0 kPa Coolant Temp 185 185 185 185 185 F Intake Air 102 102 102 102 102 F Battery Voltage 13.222 13.300 12.109 11.972 11.854 V Throttle Sensor Volt % 16.5 16.5 16.0 15.6 15.6 % Throttl Sensor #2 Volt % 48.2 48.2 47.8 47.2 47.2 % Throttle Sensor Position 0.0 0.0 0.0 0.0 0.0 % Throttle Motor DUTY 16.5 16.5 16.0 15.6 15.6 % Injector (Port) 3628 2620 2744 2744 2744 μs Injection Volume (Cylinder 1) 3.062 0.226 0.226 0.226 0.226 ml Fuel Pump Duty 58.6 58.6 58.6 58.6 58.6 % EVAP (Purge) VSV 0.0 0.0 0.0 0.0 0.0 % Evap Purge Flow 0.0 0.0 0.0 0.0 0.0 % Purge Density Learn Value 0.000 0.000 0.000 0.000 0.000 EVAP System Vent Valve OFF OFF OFF OFF OFF EVAP purge VSV OFF OFF OFF OFF OFF Purge Cut VSV Duty 0.0 0.0 0.0 0.0 0.0 % Target Air-Fuel Ratio 0.998 0.998 0.998 0.998 0.998 AF Lambda B1S1 0.999 0.999 0.999 0.999 0.999 AF Lambda B2S1 0.997 0.997 0.997 0.998 0.998 AFS Voltage B1S1 3.258 3.258 3.258 3.258 3.258 V AFS Voltage B2S1 3.251 3.251 3.251 3.253 3.253 V O2S B1S2 0.000 0.000 0.000 0.000 0.000 V O2S B2S2 0.015 0.015 0.015 0.000 0.000 V Short FT #1 0.000 0.000 0.000 0.000 0.000 % Long FT #1 8.782 4.354 -2.665 -2.665 -2.665 % Total FT #1 0.058 0.058 0.058 0.058 0.058 Sort FT #2 0.000 0.000 0.000 0.000 0.000 % Long FT #2 9.264 4.587 -2.462 -2.462 -2.462 % Total FT #2 0.062 0.062 0.062 0.062 0.062 Fuel System Status #1 OL OL OL OL OL Fuel System Status #2 OL OL OL OL OL IGN Advance 0.0 10.5 16.5 18.0 18.0 deg Knock Feedback Value -1.5 -1.5 -1.5 -1.5 -1.5 deg(CA) Knock Correct Learn Value 17.0 17.0 17.0 17.0 17.0 deg(CA) Starter Signal Close Close Close Close Close

MONITOR DESCRIPTION

The ECM continuously monitors its main and sub CPUs. This self-check ensures that the ECM is functioning properly. If outputs from the CPUs are different and deviate from the standard, the ECM will illuminate the MIL and set a DTC immediately.

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 with motor body 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 does not use a throttle cable.

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.

Example

1. When the electrical current is less than 0.5 A and the throttle actuator duty ratio is 80% or more, the ECM interprets this as the current being outside the standard range, 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 with motor body 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) [637.5 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 engine switch has been turned on (IG) (include engine running) for 1 hour or more, the engine is warmed up and conditions for ISC learning are met.

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 with motor body 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) [637.5 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 engine switch has been turned 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 with motor body assembly. The throttle position sensor provides feedback to the ECM so that the ECM can control the throttle actuator (throttle valve) appropriately in response to driver inputs.

HINT

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

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

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 with motor body assembly. The throttle position sensor provides feedback to the ECM so that the ECM can control the throttle actuator (throttle valve) appropriately in response to driver inputs.

HINT

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

The ECM determines that there is a malfunction in the electronic throttle control system when the throttle valve remains at a fixed angle despite a high drive current from the ECM. The ECM illuminates the MIL and sets 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 engine switch off. The ECM then allows the current to flow to the throttle actuator so that it can be restarted.

HINT

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

Scheme 177

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

When the power supply voltage (+BM) drops 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 sets 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 sets the DTC.

HINT

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

The accelerator pedal sensor assembly is mounted on the accelerator pedal bracket and has 2 sensor circuits: VPA (main) and VPA2 (sub). This sensor is a non-contact type. It uses Hall-effect elements in order to yield accurate signals, even in extreme conditions. The voltage, which is applied to terminals VPA and VPA2 of the ECM, varies between 0.5 V and 4.75 V in proportion to the operating angle of the accelerator pedal (throttle valve). A signal from VPA indicates the actual accelerator pedal operating angle (throttle valve opening angle) and is used for engine control. A signal from VPA2 conveys the status of the VPA circuit and is used to check the accelerator pedal sensor assembly itself.

The ECM monitors the actual accelerator pedal operating angle (throttle valve opening angle) through the signals from VPA and VPA2, and controls the throttle actuator according to these signals.

Scheme 178

HINT

When any of these DTCs are set, check the accelerator pedal sensor assembly voltage by entering the following menus: Powertrain / Engine / Data List / Accel Sensor Out No. 1 and Accel Sensor Out No. 2.

HINT

Accelerator pedal positions are expressed as voltages.

1. When either of the output voltages of VPA or VPA2 deviates from the standard range, or the difference between the output voltages of the 2 sensor circuits is less than the threshold, the ECM determines that there is a malfunction in the accelerator pedal position sensor. The ECM then illuminates the MIL and sets a DTC. Example: When the output voltage of VPA drops below 0.4 V for more than 0.5 seconds when the accelerator pedal is fully depressed, DTC P2122 is set.

Refer to DTC P2120. Refer to «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 the DTC.

Refer to DTC P2120. Refer to «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 the DTC.

HINT

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

The air fuel ratio sensor generates 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 with an integrated 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 narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, therefore the sensor activation is accelerated.

A three-way catalytic converter is used in order to convert the carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) into less harmful substances. To allow the three-way catalytic converter to function effectively, it is necessary to keep the air fuel ratio of the engine near the stoichiometric air fuel ratio.

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

Scheme 179

HINT

1. DTCs P2195 and P2196 indicate malfunctions related to the bank 1 air fuel ratio sensor circuit.
2. DTCs P2197 and P2198 indicate malfunctions related to the bank 2 air fuel ratio sensor circuit.
3. When any of these DTCs are set, check the air fuel ratio sensor output voltage by entering the following menus: Powertrain / Engine / Data List / AFS Voltage B1S1 or AFS Voltage B2S1.
4. Short-term fuel trim values can also be read using the Techstream.
5. The ECM regulates the voltages at the A1A+, A2A+, A1A- and A2A- terminals of the ECM to a constant level. Therefore, the air fuel ratio sensor output voltage cannot be confirmed without using the Techstream.
6. If an air fuel ratio sensor malfunction is detected, the ECM sets 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 rear heated oxygen sensor output voltage being less than 0.59 V, the ECM stores DTC P2196 or P2198. Alternatively, if the air fuel ratio sensor output voltage is more than 3.8 V (very lean condition) for 5 seconds despite the rear heated oxygen sensor output voltage being 0.21 V or more, DTC P2195 or P2197 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 more 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 or P2197 (stuck on high side). If the air fuel ratio sensor output is less than 0.8 mA for more than 3 seconds of cumulative time, the ECM stores DTC P2196 or P2198 (stuck on low side).

Scheme 180

HINT

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

The air fuel ratio sensor generates 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 with an integrated 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 narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, therefore the sensor activation is accelerated.

A three-way catalytic converter is used in order to convert the carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) into less harmful substances. To allow the three-way catalytic converter to function effectively, it is necessary to keep the air fuel ratio of the engine near the stoichiometric air fuel ratio.

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

1. *1: except U880F
2. *2: for U880F

HINT

1. DTCs P2195 and P2196 indicate malfunctions related to the bank 1 air fuel ratio sensor circuit.
2. DTCs P2197 and P2198 indicate malfunctions related to the bank 2 air fuel ratio sensor circuit.
3. When any of these DTCs are set, check the air fuel ratio sensor output voltage by entering the following menus: Powertrain / Engine / Data List / AFS Voltage B1S1 or AFS Voltage B2S1.
4. Short-term fuel trim values can also be read using the Techstream.
5. The ECM regulates the voltages at the A1A+, A2A+, A1A- and A2A- terminals of the ECM to a constant level. Therefore, the air fuel ratio sensor output voltage cannot be confirmed without using the Techstream.
6. If an air fuel ratio sensor malfunction is detected, the ECM sets 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 rear heated oxygen sensor output voltage being less than 0.59 V, the ECM stores DTC P2196 or P2198. Alternatively, if the air fuel ratio sensor output voltage is more than 3.8 V (very lean condition) for 5 seconds despite the rear heated oxygen sensor output voltage being 0.21 V or more, DTC P2195 or P2197 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 more 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 or P2197 (stuck on high side). If the air fuel ratio sensor output is less than 0.8*1 or 0.7*2 mA for more than 3 seconds of cumulative time, the ECM stores DTC P2196 or P2198 (stuck on low side).

1. *1: except U880F
2. *2: for U880F

See also:
• ON-VEHICLE INSPECTION [03/2012 - ] - Step 1
• ON-VEHICLE INSPECTION [03/2012 - ]
• ON-VEHICLE INSPECTION [03/2012 - ] - Step 2