| DTC Code | DTC Name |
|---|---|
| P0136 | Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2) |
| P0137 | Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2) |
| P0138 | Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2) |
DESCRIPTION
Tech Tips
Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.
In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbons (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 air fuel level. For the purpose of helping the ECM to deliver accurate air fuel ratio control, a heated oxygen sensor is used.
The heated oxygen sensor is located behind the three-way catalytic converter, 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 gas is rich. The heated oxygen sensor informs the ECM that the post-three-way catalytic converter air fuel ratio is lean (low voltage, i.e. below 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 heated oxygen sensor informs the ECM that the post-three-way catalytic converter air fuel ratio is rich (high voltage, i.e. higher than 0.45 V). The heated oxygen 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 heated oxygen sensor to determine whether the air fuel ratio after the three-way catalytic converter is rich or lean, and adjusts the fuel injection duration accordingly. Thus, if the heated oxygen sensor is working improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air fuel ratio control.
| DTC No. | DTC Detection Condition | Trouble Area |
|---|---|---|
| P0136 | Abnormal voltage output:
|
|
| P0137 | Low voltage (open):
|
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| P0138 | High voltage (short):
|
|
MONITOR DESCRIPTION
Active Air Fuel Ratio Control
The ECM usually performs air fuel ratio feedback control so that the air fuel ratio sensor output indicates a near stoichiometric air fuel level. This vehicle includes active air fuel ratio control in addition to regular air fuel ratio control. The ECM performs active air fuel ratio control to detect any deterioration in the three-way catalytic converter and heated oxygen sensor malfunctions (refer to the diagram below).
Active air fuel ratio control is performed for approximately 30 seconds while driving with a warm engine. During active air fuel ratio control, the air fuel ratio is forcibly regulated to become lean or rich by the ECM. If the ECM detects a malfunction, a DTC is stored.
Abnormal Voltage Output of Heated Oxygen Sensor (DTC P0136)
While the ECM is performing active air fuel ratio control, the air fuel ratio is forcibly regulated to become rich or lean. If the sensor is not functioning properly, the voltage output variation is small. For example, when the heated oxygen sensor voltage does not decrease to below 0.21 V or does not increase to higher than 0.59 V during active air fuel ratio control, the ECM determines that the sensor voltage output is abnormal and stores DTCs P0136.
Open or Short in Heated Oxygen Sensor Circuit (DTCs P0137 or P0138)
During active air fuel ratio control, the ECM calculates the oxygen storage capacity* of the three-way catalytic converter by forcibly regulating the air fuel ratio to become rich or lean.
If the heated oxygen sensor has an open or short circuit or the voltage output of the sensor noticeably decreases, the oxygen storage capacity indicates an extraordinarily high value. Even if the ECM attempts to continue regulating the air fuel ratio to become rich or lean, the heated oxygen sensor output does not change.
While performing active air fuel ratio control, when the target air fuel ratio is rich and the heated oxygen sensor voltage output is below 0.21 V (lean), the ECM interprets this as an abnormally low sensor output voltage and stores DTC P0137. When the target air fuel ratio is lean and the voltage output is higher than 0.59 V (rich) during active air fuel ratio control, the ECM determines that the sensor voltage output is abnormally high, and stores DTC P0138.
*: The three-way catalytic converter has the capability to store oxygen. The oxygen storage capacity and the emission purification capacity of the three-way catalytic converter are mutually related. The ECM determines whether the catalyst has deteriorated, based on the calculated oxygen storage capacity value Click here.
MONITOR STRATEGY
| Required Sensors/Components (Main) | Heated oxygen sensor (sensor 2) |
| Required Sensors/Components (Related) | Crankshaft position sensor Engine coolant temperature sensor Mass air flow meter sub-assembly Throttle position sensor Air fuel ratio sensor |
| Frequency of Operation | Once per driving cycle |
TYPICAL ENABLING CONDITIONS
| Active air fuel ratio control | Executing |
| Active air fuel ratio control begins when all of the following conditions are met: | - |
| Auxiliary battery voltage | 11 V or higher |
| Engine coolant temperature | 75°C (167°F) or higher |
| Idling | OFF |
| Engine speed | Less than 4000 rpm |
| Air fuel ratio sensor status | Activated |
| Fuel system status | Closed loop |
| Engine load | 10% or more, and less than 70% |
TYPICAL MALFUNCTION THRESHOLDS
| Either of the following conditions is met: | 1 or 2 |
| 1. Both of following conditions met | (a) and (b) |
| (a) Commanded air fuel ratio | 14.3 or less |
| (b) Heated oxygen sensor voltage | 0.21 V or higher, and below 0.59 V |
| 2. Both of following conditions met | (c) and (d) |
| (c) Commanded air fuel ratio | 14.9 or more |
| (d) Heated oxygen sensor voltage | 0.21 V or higher, and below 0.59 V |
| Both of following conditions met | (a) and (b) |
| (a) Commanded air fuel ratio | 14.3 or less |
| (b) Heated oxygen sensor voltage | Below 0.21 V |
| Both of following conditions met | (a) and (b) |
| (a) Commanded air fuel ratio | 14.9 or more |
| (b) Heated oxygen sensor voltage | Higher than 0.59 V |
CONFIRMATION DRIVING PATTERN
This confirmation driving pattern is used in the "Perform Confirmation Driving Pattern" procedure of the following diagnostic troubleshooting procedure.
Performing this confirmation driving pattern will activate the heated oxygen sensor monitor (the catalyst monitor is performed simultaneously). This is very useful for verifying the completion of a repair.
Connect the intelligent tester to the DLC3.
Turn the power switch on (IG) and turn the tester on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC operation).
Turn the power switch off and wait for at least 30 seconds.
Turn the power switch on (IG) and turn the tester on [A].
Put the engine in inspection mode (maintenance mode) Click here.
Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher [B].
Drive the vehicle at 75 to 120 km/h (47 to 75 mph) for 10 minutes or more [C].
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
Enter the following menus: Powertrain / Engine and ECT / DTC [D].
Read the pending DTCs.
Tech Tips
If a pending DTC is output, the system is malfunctioning.
If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTC: P0136, P0137 or P0138.
Check the DTC judgment result.
| Tester Display | Description |
|---|---|
| NORMAL |
|
| ABNORMAL |
|
| INCOMPLETE |
|
| N/A |
|
Tech Tips
If the judgment result shows NORMAL, the system is normal.
If the judgment result shows ABNORMAL, the system has a malfunction.
If the judgment result shows INCOMPLETE or N/A, perform steps [C] and [D] again.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
Tech Tips
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 sensor, heated oxygen 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.
Turn the power switch on (IG) and turn the tester on.
Put the engine in inspection mode (maintenance mode) Click here.
Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.
Idle the engine for 5 minutes or more with park (P) selected.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / All Data / AFS Voltage B1S1 and O2S B1S2.
Perform the Active Test operation with the engine in an idling.
Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the tester.
Tech Tips
The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 12.5%.
Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
| Tester Display (Sensor) | Injection Volume | Status | Voltage |
|---|---|---|---|
| AFS Voltage B1S1 (Air fuel ratio) |
12.5% | Rich | Below 3.1 V |
| -12.5% | Lean | Higher than 3.4 V | |
| O2S B1S2 (Heated oxygen) |
12.5% | Rich | Higher than 0.55 V |
| -12.5% | Lean | Below 0.4 V |
Note
The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
| Case | Air Fuel Ratio Sensor (Sensor 1) Output Voltage | Heated Oxygen Sensor (Sensor 2) Output Voltage | Main Suspected Trouble Area | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 |
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- | ||||||||||||
| 2 |
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| 3 |
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| 4 |
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Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the air fuel ratio and heated oxygen sensors.
To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / All Data / AFS Voltage B1S1 and O2S B1S2.
Note
Inspect the fuses for circuits related to this system before performing the following inspection procedure.
Tech Tips
Sensor 1 refers to the sensor closest to the engine assembly.
Sensor 2 refers to the sensor farthest away from the engine assembly.
Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, 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.
PROCEDURE
READ OUTPUT DTC (DTC P0136, P0137 OR P0138)
Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / DTC.
Read the DTCs.
| Result | Proceed to |
|---|---|
| DTC P0138 is output | A |
| DTC P0137 is output | B |
| DTC P0136 is output | C |
| DTC P0136, P0137 or P0138 and other DTCs are output | D |
Tech Tips
If any DTCs other than P0136, P0137 or P0138 are output, troubleshoot those DTCs first.
| B |
|
CHECK FOR EXHAUST GAS LEAK Click here |
| C |
|
PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME FOR A/F SENSOR) Click here |
| D |
|
GO TO DTC CHART Click here |
| A |
|
READ VALUE USING INTELLIGENT TESTER (O2S B1S2)
Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Put the engine in inspection mode (maintenance mode) Click here.
Start the engine.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
Tech Tips
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.
Allow the engine to idle.
Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / O2S B1S2.
Read the heated oxygen sensor output voltage while idling.
| Result | Proceed to |
|---|---|
| 1.0 V or higher | A |
| Below 1.0 V | B |
| B |
|
PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME FOR A/F SENSOR) Click here |
| A |
|
INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)
| *a | Component without harness connected (Heated Oxygen Sensor (Sensor 2)) |
Disconnect the heated oxygen sensor connector.
Measure the resistance according to the value(s) in the table below.
| Standard Resistance | |||||||||
|---|---|---|---|---|---|---|---|---|---|
|
| NG |
|
REPLACE HEATED OXYGEN SENSOR Click here |
| OK |
|
CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)
Turn the power switch off and wait for 5 minutes or more.
Disconnect the ECM connector.
Measure the resistance according to the value(s) in the table below.
| Standard Resistance | ||||||
|---|---|---|---|---|---|---|
|
| OK |
|
REPLACE ECM Click here |
| NG |
|
REPAIR OR REPLACE HARNESS OR CONNECTOR |
PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)
Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Put the engine in inspection mode (maintenance mode) Click here.
Start the engine.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
Tech Tips
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.
Allow the engine to idle.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / All Data / AFS Voltage B1S1 and O2S B1S2.
Change the fuel injection volume using the tester and monitor the voltage output of the air fuel ratio and heated oxygen sensors displayed on the tester.
Tech Tips
The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 12.5%.
The air fuel ratio sensor is displayed as AFS Voltage B1S1, and the heated oxygen sensor is displayed as O2S B1S2 on the tester.
The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.
| Tester Display (Sensor) | Voltage Variation | Proceed to |
|---|---|---|
| AFS Voltage B1S1 (Air fuel ratio) |
Alternates between higher and below 3.3 V | OK |
| Remains at higher than 3.3 V | NG | |
| Remains at below 3.3 V | NG |
Tech Tips
A normal heated oxygen sensor voltage (O2S B1S2) reacts in accordance with increases and decreases in fuel injection volumes. When the air fuel ratio sensor (AFS Voltage B1S1) voltage remains at either below or higher than 3.3 V despite the heated oxygen sensor indicating a normal reaction, the air fuel ratio sensor is malfunctioning.
| NG |
|
REPLACE AIR FUEL RATIO SENSOR Click here |
| OK |
|
INSPECT AIR FUEL RATIO SENSOR
Tech Tips
This air fuel ratio sensor test is to check the air fuel ratio sensor current during the fuel-cut. When the sensor is normal, the sensor current will indicate below 2.2 mA in this test.
Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Clear the DTCs Click here.
Put the engine in inspection mode (maintenance mode) Click here.
Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or more.
Drive the vehicle at 75 km/h (47 mph) or more for 10 minutes or more.
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
Stop the vehicle.
Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / AFS Current B1S1 and Fuel Cut Condition.
Drive the vehicle at 75 km/h (47 mph) or more and decelerate the vehicle for 5 seconds or more. Perform this 3 times.
Tech Tips
While "Fuel Cut Condition" on the Data List is ON, fuel-cut control is being executed.
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
| *a | 75 km/h |
| *b | 0 km/h |
| *c | 10 minutes or more |
| *d | 5 seconds or more |
Read the value of the air fuel ratio sensor current while the fuel-cut operation is being performed.
| Standard current |
|---|
| Below 2.2 mA |
Tech Tips
To measure the air fuel ratio sensor current precisely, perform the fuel-cut operation as long as possible.
If it is difficult to measure the air fuel ratio sensor current, use the snapshot function of the intelligent tester.
| OK |
|
REPLACE HEATED OXYGEN SENSOR Click here |
| NG |
|
REPLACE AIR FUEL RATIO SENSOR Click here |
PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)
Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Put the engine in inspection mode (maintenance mode) Click here.
Start the engine.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
Tech Tips
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.
Allow the engine to idle.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / All Data / O2S B1S2.
Change the fuel injection volume using the tester, monitoring the voltage output of the heated oxygen sensor displayed on the tester.
Tech Tips
The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 12.5%.
The heated oxygen sensor has a maximum output delay of approximately 20 seconds.
| Standard |
|---|
| Fluctuates between 0.4 V or less and 0.55 V or higher. |
| NG |
|
CHECK FOR EXHAUST GAS LEAK Click here |
| OK |
|
PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)
Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Put the engine in inspection mode (maintenance mode) Click here.
Start the engine.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
Tech Tips
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.
Allow the engine to idle.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / All Data / AFS Voltage B1S1 and O2S B1S2.
Change the fuel injection volume using the tester and monitor the voltage output of the air fuel ratio and heated oxygen sensors displayed on the tester.
Tech Tips
The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 12.5%.
The air fuel ratio sensor is displayed as AFS Voltage B1S1, and the heated oxygen sensor is displayed as O2S B1S2 on the tester.
The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.
If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.
| Tester Display (Sensor) | Voltage Variation | Proceed to |
|---|---|---|
| AFS Voltage B1S1 (Air fuel ratio) |
Alternates between higher and below 3.3 V | OK |
| Remains at higher than 3.3 V | NG | |
| Remains at below 3.3 V | NG |
Tech Tips
A normal heated oxygen sensor voltage (O2S B1S2) reacts in accordance with increases and decreases in fuel injection volumes. When the air fuel ratio sensor (AFS Voltage B1S1) voltage remains at either below or higher than 3.3 V despite the heated oxygen sensor indicating a normal reaction, the air fuel ratio sensor is malfunctioning.
| OK |
|
CHECK ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO (FUEL INJECTOR ASSEMBLY, FUEL SYSTEM, INTAKE SYSTEM, ETC.) Click here |
| NG |
|
REPLACE AIR FUEL RATIO SENSOR Click here |
CHECK FOR EXHAUST GAS LEAK
Check for exhaust gas leaks.
| OK |
|---|
| No gas leaks. |
| NG |
|
REPAIR OR REPLACE EXHAUST GAS LEAK POINT |
| OK |
|
INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
Inspect the heated oxygen sensor Click here.
| NG |
|
REPLACE HEATED OXYGEN SENSOR Click here |
| OK |
|
CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)
Disconnect the heated oxygen sensor connector.
Disconnect the ECM connector.
Measure the resistance according to the value(s) in the table below.
| Standard Resistance | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
| NG |
|
REPAIR OR REPLACE HARNESS OR CONNECTOR |
| OK |
|
REPLACE HEATED OXYGEN SENSOR
Replace the heated oxygen sensor Click here.
| NEXT |
|
PERFORM CONFIRMATION DRIVING PATTERN
Perform Confirmation Driving Pattern.
| NEXT |
|
CHECK WHETHER DTC OUTPUT RECURS (DTC P0136, P0137 OR P0138)
Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTCs: P0136, P0137 or P0138.
Check the DTC judgment result is NORMAL. If it is INCOMPLETE, perform the drive pattern adding the vehicle speed.
| Result | Proceed to |
|---|---|
| ABNORMAL (DTC P0136, P0137 or P0138 is output) |
A |
| NORMAL (DTC is not output) |
B |
| A |
|
REPLACE AIR FUEL RATIO SENSOR Click here |
| B |
|
END |
REPLACE AIR FUEL RATIO SENSOR
Replace the air fuel ratio sensor Click here.
| NEXT |
|
PERFORM CONFIRMATION DRIVING PATTERN
Perform Confirmation Driving Pattern.
| NEXT |
|
CHECK WHETHER DTC OUTPUT RECURS (DTC P0136 OR P0138)
Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTCs: P0136 or P0138.
Check the DTC judgment result is NORMAL. If it is INCOMPLETE, perform the driving pattern again and increase the vehicle speed.
| Result | Proceed to |
|---|---|
| ABNORMAL (DTC P0136 or P0138 is output) |
A |
| NORMAL (DTC is not output) |
B |
| A |
|
REPLACE HEATED OXYGEN SENSOR Click here |
| B |
|
END |