3Gr-Fse Engine Control System. Dtc P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)

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 (Three-Way Catalytic Converter) 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 air-fuel level. For the purpose of helping the ECM to deliver accurate air-fuel ratio control, a Heated Oxygen (HO2) sensor is used.
The HO2 sensor is located behind the TWC, and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen concentration even when the intake air volume is low (the exhaust gas temperature is low).
When the air-fuel ratio becomes lean, the oxygen concentration in the exhaust has is rich. The HO2 sensor informs the ECM that the post-TWC air-furl ratio is lean (low voltage, i.e. less than 0.45 V).
Conversely, when the air-fuel ratio is richer than the stoichiometric air-fuel level, the oxygen concentration in the exhaust gas becomes lean. The HO2 sensor informs the ECM that the post-TWC air-fuel ratio is rich (high voltage, i.e. more than 0.45 V). The HO2 sensor has the property of changing its output voltage drastically when the air-fuel ratio is close to the stoichiometric level.
The ECM uses the supplementary information from the HO2 sensor to determine whether the air-fuel ratio after the TWC is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the HO2 sensor is working improperly due to internal malfunctions. The ECM is unable to compensate for deviations in the primary air-fuel ratio control.

Lexus Gs430, Gs300. Uzs190 Grs190.3Gr-Fse Engine Control System.Sfi System.
Dtc
P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)

DTC No.

DTC Detection Condition

Trouble Area

P0136
P0156

Abnormal voltage output:
During active air-fuel ratio control, following conditions (a) and (b) met for certain period of time (1 trip detection logic):

(a) Heated Oxygen (HO2) sensor voltage does not decrease to less than 0.45 V
(b) HO2 sensor voltage does not increase to more than 0.6 V

Open or short in HO2 sensor (bank 1, 2 sensor 2) circuit
HO2 sensor (bank 1, 2 sensor 2)
HO2 sensor heater (bank 1, 2 sensor 2)
Air-Fuel Ratio (A/F) sensor (bank 1, 2 sensor 1)
EFI MAIN relay
Gas leakage from exhaust system

P0138
P0139
P0158
P0159

Fuel-cut HO2 sensor voltage:
Either of following conditions (a) or (b) met (1 trip detection logic):

(a) Duration until HO2 sensor voltage drops to 0.2 V after fuel-cut start 00.7 seconds or more
(b) Both following conditions (1) and (2) met:

(1) Rear HO2 sensor voltage when fuel-cut start 0.5 V or more
(2) Duration that HO2 sensor voltage to 0.2 to 0.35 V 1 second or more

Either of following conditions met:

HO2 sensor voltage does not decrease below 0.2 V immediately when fuel-cut performed
HO2 sensor output voltage 1.2 V or more for 10 seconds

Short in HO2 sensor (bank 1, 2 sensor 2) circuit
HO2 sensor (bank 1, 2 sensor 2)
ECM internal circuit malfunction

MONITOR DESCRIPTION

The ECM monitors the rear Heated Oxygen (HO2) sensor to check for the following malfunctions. If any of the malfunctions are detected, the ECM illuminates the MIL and sets a DTC.

The HO2 sensor output voltage remains above 0.45 V (rich) or below 0.45 V (lean) while the vehicle is accelerated and decelerated for 8 minutes.
The HO2 sensor output voltage remains at below 0.05 V, for a long period of time while the vehicle is driven.
The HO2 sensor output voltage does not decrease below 0.2 V (extremely lean condition) within 7 seconds after fuel-cut is performed while the vehicle is decelerated. The ECM interprets this as the sensor response having deteriorated.

WIRING DIAGRAM

CONFIRMATION DRIVING PATTERN

(a) Connect the intelligent tester to the DLC3.

(b) Switch the ECM From normal mode to check mode using the tester (Click here).

(d) Drive the vehicle at 60 km/h (38 mph) or more for 40 seconds or more.

(e) Let the engine idle for 10 seconds or more.

(f) Perform steps (d) and (e) 12 times.

HINT:

If a malfunction exists, the MIL illuminates during step (f).

NOTICE:

If the conditions in this test are not strictly followed, malfunctions may not be detected. If you do not have the intelligent tester, turn the engine switch off after performing steps from (c) to (f), then perform steps (c) to (f) again.

INSPECTION PROCEDURE

HINT:

Intelligent tester only:

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 an intelligent tester.

Connect the intelligent tester to the DLC3.
Start the engine and turn the tester ON.
Warm up the engine at engine speed of 2,500 rpm for approximately 90 seconds.
On the tester, enter the following menus: Power train / Engine / Active Test / Control the Injection Volume for A/F Sensor.
Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) 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.

Standard:
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 Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20 seconds.

Case	A/F Sensor (Sensor 1) Output Voltage	HO2 Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
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.
To display the graph, enter the following menus: Power train / Engine / Active Test / Control the Injection Volume for A/F Sensor and Data List / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2.

HINT:

If other DTCs relating to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may have an open circuit.
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.
If the OX1B wire from the ECM connector is short-circuited to the +B wire, DTC P0136 will be set.
If the OX2B wire from the ECM connector is short-circuited to the +B wire, DTC P0156 will be set.

1.READ OUTPUT DTC

Connect the intelligent tester to the DLC3.

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

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

Read DTCs.

Result:
Display (DTC Output)
Proceed to
P0138 or P0158
A
P0136 or P0156
B

Result:
Display (DTC Output)	Proceed to
P0138 or P0158	A
P0136 or P0156	B

Go to step 7

A

2.READ VALUE USING INTELLIGENT TESTER (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR)

Connect the intelligent tester to the DLC3.

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

Enter the following menus: Power train / Engine / Data List / O2S B1 S2 or O2S B2 S2.

Allow the engine to idle.

Read the Heated Oxygen (HO2) sensor output voltage while idling.

Result:
HO2 Sensor Output Voltage
Proceed to
More than 1.2 V
A
Less than 1.0 V
B

Result:
HO2 Sensor Output Voltage	Proceed to
More than 1.2 V	A
Less than 1.0 V	B

Go to step 5

A

3.CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)

Turn the engine switch off and wait for 5 minutes.

Disconnect the A7 ECM connector.

Measure the resistance.
Standard Resistance:
Tester Connection
Specified Condition
HT1B (A7-2) - OX1B (A7-28)
10 kΩ or higher
HT2B (A7-1) - OX2B (A7-17)
10 kΩ or higher

Standard Resistance:
Tester Connection	Specified Condition
HT1B (A7-2) - OX1B (A7-28)	10 kΩ or higher
HT2B (A7-1) - OX2B (A7-17)	10 kΩ or higher

Reconnect the ECM connector.

Go to step 4

REPLACE ECM

4.INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)

Disconnect the L34 or L57 HO2 sensor connector.

Measure the resistance.
Standard resistance (Bank 1 sensor 2):
Tester Connection
Specified Condition
+B (2) - E (4)
10 kΩ or higher
+B (2) - OX1B (3)
10 kΩ or higher
Standard resistance (Bank 2 sensor 2):
Tester Connection
Specified Condition
+B (2) - E2 (4)
10 kΩ or higher
+B (2) - OX2B (3)
10 kΩ or higher

Standard resistance (Bank 1 sensor 2):
Tester Connection	Specified Condition
+B (2) - E (4)	10 kΩ or higher
+B (2) - OX1B (3)	10 kΩ or higher

Standard resistance (Bank 2 sensor 2):
Tester Connection	Specified Condition
+B (2) - E2 (4)	10 kΩ or higher
+B (2) - OX2B (3)	10 kΩ or higher

REPLACE HEATED OXYGEN SENSOR

OK

5.PERFORM CONFIRMATION DRIVING PATTERN

NEXT

6.CHECK WHETHER DTC OUTPUT RECURS (DTC P0138 or P0158)

On the intelligent tester, enter the following menus: Power train / Engine / DTC.

Read DTCS.

Result:
Display (DTC Output)
Proceed to
P0138 or P0158
A
No output
B

Result:
Display (DTC Output)	Proceed to
P0138 or P0158	A
No output	B

CHECK FOR INTERMITTENT PROBLEMS

REPLACE HEATED OXYGEN SENSOR

7.READ VALUE USING INTELLIGENT TESTER (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR)

Connect the intelligent tester to the DLC3.

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

Start the engine.

Enter the following menus: Power train / Engine / Data List / O2S B1 S2 or O2S B1 S2.

After warming up the engine, run the engine at an engine speed of 2,500 rpm for 3 minutes.

Read the output voltage of the HO2 sensor when the engine rpm is suddenly increased.

HINT:

Quickly accelerate the engine to 4,000 rpm 3 times using the accelerator pedal.

Standard voltage:: Fluctuates between 0.4 V or less and 0.5 V or more.

Go to step 14

OK

8.PERFORM CONFIRMATION DRIVING PATTERN

NEXT

9.CHECK WHETHER DTC OUTPUT RECURS (DTC P0136 or P0156)

On the intelligent tester, enter the following menus: Power train / Engine / DTC.

Read DTCs.

Result:
Display (DTC Output)
Proceed to
P0136 or P0156
A
No output
B

CHECK FOR INTERMITTENT PROBLEMS

A

10.REPLACE HEATED OXYGEN SENSOR

NEXT

11.PERFORM CONFIRMATION DRIVING PATTERN

NEXT

12.CHECK WHETHER DTC OUTPUT RECURS (DTC P0136 or P0156)

On the intelligent tester, enter the following menus: Power train / Engine / DTC.

Read DTCs.

Result:
Display (DTC Output)
Proceed to
P0136 or P0156
A
No output
B

REPAIR COMPLETED

A

13.PERFORM ACTIVE TEST USING INTELLIGENT TESTER (INJECTION VOLUME)

Connect the intelligent tester to the DLC3.

Start the engine and turn the tester ON.

Warm up the engine.

Enter the following menus: Power train / Engine / Active Test / Control the Injection Volume.

Change the fuel injection volume using the tester, monitoring the output voltage of Air-Fuel Ratio (A/F) and HO2 sensor displayed on the tester.

HINT:

Change the fuel injection volume within the range of -12 % and +12 %. The injection volume can be changed in 1 % graduations within the range.
The A/F sensor is displayed as AFS B1 S1 or AFS B2 S1, and the HO2 sensor is displayed as O2S B1 S2 or O2S B2 S2, on the intelligent testers.

Result:
Tester Display (Sensor)	Voltage Variation	Proceed to
AFS B1S1 (A/F) AFS B2S1 (A/F)	Alternates between more and less than 3.3 V	OK
AFS B1S1 (A/F) AFS B2S1 (A/F)	Remains at more than 3.3 V	NG
AFS B1S1 (A/F) AFS B2S1 (A/F)	Remains at less than 3.3 V	NG

HINT:

A normal HO2 sensor voltage (O2S B1 S2 or O2S B2 S2) reacts in accordance with increases and decreases in fuel injection volumes. When the A/F sensor voltage remains at either less or more than 3.3 V despite the HO2 sensor indicating a normal reaction, the A/F sensor is malfunctioning.

REPLACE AIR FUEL RATIO SENSOR

CHECK AND REPAIR EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO (INJECTOR, FUEL PRESSURE, GAS LEAKAGE FROM EXHAUST SYSTEM, ETC.)

14.CHECK EXHAUST GAS LEAKAGE

OK:: No gas leakage.

REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

OK

15.INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

Disconnect the L34 or L57 HO2 sensor connector.

Measure the resistance.
Standard resistance (Bank 1 sensor 2):
Tester Connection
Specified Condition
HT (1) - +B (2)
5 to 10 Ω at 20°C (68°F)
HT (1) - E (4)
10 kΩ or higher
Standard resistance (Bank 2 sensor 2):
Tester Connection
Specified Condition
HT2B (1) - +B (2)
5 to 10 Ω at 20°C (68°F)
HT2B (1) - E2 (4)
10 kΩ or higher

REPLACE HEATED OXYGEN SENSOR

OK

16.INSPECT INTEGRATION RELAY (EFI MAIN RELAY)

Remove the integration relay from the engine room No. 2 junction block.

Measure the resistance of the EFI MAIN relay.
Standard resistance:
Terminal Connection
Specified Condition
2A-8 - 2A-5
10 kΩ or higher
2A-8 - 2A-5
Below 1 Ω
(when battery voltage applied to terminals 2A-7 and 2A-6)

Reinstall the integration relay.

REPLACE INTEGRATION RELAY

OK

17.CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)

Disconnect the L34 and L57 HO2 sensor connector.

Turn the engine switch on (IG).

Measure the voltage between the +B terminal of the HO2 sensor connector and body ground.
Standard voltage:
Terminal Connection
Specified Condition
+B (L34-2) - Body ground
9 to 14 V
+B (L57-2) - Body ground
9 to 14 V

Turn the engine switch off.

Disconnect the A7 ECM connector.

Measure the resistance.

Standard resistance (Check for open):

Terminal Connection	Specified Condition
HT (L34-1) - HT1B (A7-2)	Below 1 Ω
OX1B (L34-3) - OX1B (A7-28)	Below 1 Ω
E (L34-4) - O1B- (A7-29)	Below 1 Ω
HT2B (L57-1) - HT2B (A7-1)	Below 1 Ω
OX2B (L57-3) - OX2B (A7-17)	Below 1 Ω
E2 (L57-4) - O2B- (A7-18)	Below 1 Ω

Standard resistance (Check for short):

Terminal Connection	Specified Condition
HT (L34-1) or HT1B (A7-2) - Body ground	10 kΩ or higher
OX1B (L34-3) - OX1B (A7-28) - Body ground	10 kΩ or higher
E (L34-4) or O1B- (A7-29) - Body ground	10 kΩ or higher
HT2B (L57-1) or HT2B (A7-1) - Body ground	10 kΩ or higher
OX2B (L57-3) or OX2B (A7-17) - Body ground	10 kΩ or higher
E2 (L57-4) or O2B- (A7-18) - Body ground	10 kΩ or higher

Reconnect the HO2 sensor connector.

Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS AND CONNECTOR

REPLACE HEATED OXYGEN SENSOR

Tester Connection	Specified Condition
HT (1) - +B (2)	5 to 10 Ω at 20°C (68°F)
HT (1) - E (4)	10 kΩ or higher

Tester Connection	Specified Condition
HT2B (1) - +B (2)	5 to 10 Ω at 20°C (68°F)
HT2B (1) - E2 (4)	10 kΩ or higher

Terminal Connection	Specified Condition
2A-8 - 2A-5	10 kΩ or higher
2A-8 - 2A-5	Below 1 Ω (when battery voltage applied to terminals 2A-7 and 2A-6)

Terminal Connection	Specified Condition
+B (L34-2) - Body ground	9 to 14 V
+B (L57-2) - Body ground	9 to 14 V