The A/F 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 time. If the A/F sensor malfunctions, the ECM is unable to control the air-fuel ratio accurately.

The A/F sensor is the 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 narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte though the alumina, 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 TWC is used. For the most efficient use of the TWC, 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 A/F sensor is the current output element, a current is converted to a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.

Dtc P2195 Oxygen (A/F) Sensor Signal Stuck Lean (Bank 1 Sensor 1). 4GR-FSE ENGINE CONTROL SYSTEM. Lexus IS250 IS220d GSE20 ALE20

DTC No.	DTC Detection Condition	Trouble Area
P2195 P2197	Conditions (a) and (b) continue for 2 seconds or more (2 trip detection logic): (a) Air-Fuel Ratio (A/F) sensor voltage more than 3.8 V (b) Heated Oxygen (HO2) sensor voltage 0.15 V or more	Open or short in A/F sensor (bank 1, 2 sensor 1) circuit A/F sensor (bank 1, 2 sensor 1) A/F sensor (bank 1, 2 sensor 1) heater A/F HTR relay A/F sensor heater and relay circuits Air induction system Fuel pressure Injector ECM
P2195 P2197	While fuel-cut operation performed (during vehicle deceleration), air-fuel ratio (A/F) sensor current 3.6 mA or more for 3 seconds (2 trip detection logic)	A/F sensor ECM
P2196 P2198	Conditions (a) and (b) continue for 2 seconds or more (2 trip detection logic): (a) A/F sensor voltage less than 2.8 V (b) HO2 sensor voltage less than 0.85 V	Open or short in A/F sensor (bank 1, 2 sensor 1) circuit A/F sensor (bank 1, 2 sensor 1) A/F sensor (bank 1, 2 sensor 1) heater A/F HTR relay A/F sensor heater and relay circuits Air induction system Fuel pressure Injector ECM
P2196 P2198	While fuel-cut operation performed (during vehicle deceleration), air-fuel ratio (A/F) sensor current 0.4 mA for 3 seconds (2 trip detection logic)	A/F sensor ECM

HINT:

DTCs P2195 and P2196 indicate malfunctions related to bank 1 A/F sensor circuit.

DTCs P2197 and P2198 indicate malfunctions related to bank 2 A/F sensor circuit.

Bank 1 refers to the bank that includes cylinder No. 1.

Bank 2 refers to the bank that includes cylinder No. 2.

When any of these DTCs are set, check the A/F sensor output voltage by entering the following menus on the intelligent tester: Power train / Engine / Data List / AFS B1 S1 or AFS B2 S1.

Short-term fuel trim values can also be read using an intelligent tester.

The ECM regulates the voltages at the A1A+, A2A+, A1A- and A2A- terminals of the ECM to a constant level. Therefore, the A/F sensor output voltage cannot be confirmed without using the intelligent tester.

If a A/F sensor malfunction is detected, the ECM sets a DTC.

WIRING DIAGRAM

Dtc P2195 Oxygen (A/F) Sensor Signal Stuck Lean (Bank 1 Sensor 1). 4GR-FSE ENGINE CONTROL SYSTEM. Lexus IS250 IS220d GSE20 ALE20

CONFIRMATION DRIVING PATTERN

This confirmation driving pattern is used in steps 2, 4, 7, 17 and 21 of the following diagnostic troubleshooting procedure when using an intelligent tester.

Dtc P2195 Oxygen (A/F) Sensor Signal Stuck Lean (Bank 1 Sensor 1). 4GR-FSE ENGINE CONTROL SYSTEM. Lexus IS250 IS220d GSE20 ALE20

Connect an intelligent tester to the DLC3.

Turn the engine switch on (IG).

Turn the tester ON.

Clear DTCs.

Start the engine, and warm it up until the ECT reaches 75°C (167°F) or higher (Procedure "A").

On the intelligent tester, enter the following menus to check the fuel-cut status: Power train / Engine / Data List / Idle Fuel Cut.

Drive the vehicle at between 60 km/h (38 mph) and 120 km/h (75 mph) for at least 10 minutes (Procedure "B").

Change the transmission to 2nd gear (Procedure "C").

Drive the vehicle at proper vehicle speed to perform fuel-cut operation (refer to the following HINT ) (Procedure "D").

HINT:

Fuel-cut is performed when the following conditions are met:

Accelerator pedal fully released.

Engine speed is 2,500 rpm or more (fuel injection returns at 1,000 rpm).

Accelerate the vehicle to 64 km/h (40 rpm) or more by depressing the accelerator pedal for at least 10 seconds (Procedure "E").

Soon after performing procedure E above, release the accelerator pedal for at least 4 seconds without depressing the brake pedal, in order to execute fuel-cut control (Procedure "F").

Allow the vehicle to decelerate until the vehicle speed declines to less than 10 km/h (6 mph).

Repeat procedure from C through F above at least 3 times in one driving cycle.

HINT:

Completion of all A/F sensor monitors is required to change the value in TEST RESULT.

CAUTION:

Strictly observe posted speed limits, traffic laws, and road conditions when performing these drive patterns.

INSPECTION PROCEDURE

HINT:

Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the Air-fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the Control the Injection Volume for A/F Sensor operation using the intelligent tester.

Connect the intelligent tester to the DLC3.

Start the engine and turn the tester ON.

Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.

On the intelligent tester, enter the following menus: Power train / Engine / Active Test / Control the Injection Volume for A/F Sensor.

Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).

Monitor the output voltages of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the tester.

HINT:

The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5 % or increases the injection volume by 25 %.

Each sensor reacts in accordance with increases in the fuel injection volume.

Tester Display (Sensor)	Injection Volume	Status	Voltage
AFS B1S1 or AFS B2S1 (A/F)	+25 %	Rich	Less than 3.0
AFS B1S1 or AFS B2S1 (A/F)	-12.5 %	Lean	More than 3.35
O2S B1S2 or O2S B2S2 (HO2)	+25 %	Rich	More than 0.55
O2S B1S2 or O2S B2S2 (HO2)	-12.5 %	Lean	Less than 0.4

NOTICE:

The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the HO2S (sensor 2) output has a maximum of 20 seconds of delay.

Case	A/F Sensor (Sensor 1) Output Voltage	HO2 Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Areas
1	Injection Volume +25 % -12.5 %	Injection Volume +25 % -12.5 %	-
1	Output Voltage More than 3.35 V Less than 3.0 V	Output Voltage More than 0.55 V Less than 0.4 V	-
2	Injection Volume +25 % -12.5 %	Injection Volume +25 % -12.5 %	A/F sensor A/F sensor heater A/F sensor circuit
2	Output Voltage Almost no reaction	Output Voltage More than 0.55 V Less than 0.4 V	A/F sensor A/F sensor heater A/F sensor circuit
3	Injection Volume +25 % -12.5 %	Injection Volume +25 % -12.5 %	HO2 sensor HO2 sensor heater HO2 sensor circuit
3	Output Voltage More than 3.35 V Less than 3.0 V	Output Voltage Almost no reaction	HO2 sensor HO2 sensor heater HO2 sensor circuit
4	Injection volume +25 % -12.5 %	Injection Volume +25 % -12.5 %	Injector Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely lean or rich)
4	Output Voltage Almost no reaction	Output Voltage Almost no reaction

Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.

The following A/F Control procedure enables the technician to check and graph the voltage output of both the heated oxygen sensors. To display the graph, select the following menu items on the tester: View / Line Graph.

HINT:

Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred .

A low A/F sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would cause the engine to run rich.

A high A/F sensor voltage could be caused by a lean air-fuel mixture. Check for conditions that would cause the engine to run lean.

1.CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO P2195, P2196, 2197 OR P2198)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG).

Turn the tester ON

Enter the following menus: Power train / Engine / DTC.

Read DTCs.

Result:
Display (DTC Output) Proceed to
P2195, P2196, P2197, or P2198 A
P2195, P2196, P2197, or P2198 and other DTCs B

HINT:

If any DTCs other than P2195, P2196, P2197 or P2198 are output, troubleshoot those DTCs first.

Go to step 12

OK

3.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Dtc P2195 Oxygen (A/F) Sensor Signal Stuck Lean (Bank 1 Sensor 1). 4GR-FSE ENGINE CONTROL SYSTEM. Lexus IS250 IS220d GSE20 ALE20

Disconnect the E38 or E42 A/F sensor connector.

Measure the resistance of the A/F sensor connector.

Standard resistance (Bank 1 sensor 1):
Tester Connection Condition Specified Condition
HA1A (1) - +B (2) 20°C (68°F) 1.8 Ω to 3.4 Ω
HA1A (1) - A1A- (4) - 10 kΩ or higher

Standard resistance (Bank 2 sensor 1):
Tester Connection Condition Specified Condition
HA2A (1) - +B (2) 20°C (68°F) 1.8 Ω to 3.4 Ω
HA2A (1) - A2A- (4) - 10 kΩ or higher

Reconnect the A/F sensor connector.

Go to step 11

A

14.REPLACE AIR FUEL RATIO SENSOR

NEXT

15.PERFORM CONFIRMATION DRIVING PATTERN

NEXT

16.CHECK WHETHER DTC OUTPUT RECURS (DTC P2195, P2196, P2197 OR P2198)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG) and turn the tester ON.

Read DTCs using the intelligent tester.

Enter the following menus: Power train / Engine / DTC.

Result:
Display (DTC Output) Proceed to
No output A
P2195, P2196, P2197 or P2198 (A/F sensor pending DTCs) B

REPLACE ECM

END

LEXUS IS250, IS220d / GSE20 ALE20

4GR-FSE ENGINE CONTROL SYSTEM

Lexus IS250 IS220d GSE20 ALE20

SFI SYSTEM

Tester Connection	Condition	Specified Condition
HA1A (1) - +B (2)	20°C (68°F)	1.8 Ω to 3.4 Ω
HA1A (1) - A1A- (4)	-	10 kΩ or higher

Tester Connection	Condition	Specified Condition
HA2A (1) - +B (2)	20°C (68°F)	1.8 Ω to 3.4 Ω
HA2A (1) - A2A- (4)	-	10 kΩ or higher