P0157
1UR-FSE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0136: Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)
DTC P0136 - Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)
DTC P0137 - Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2)
DTC P0138 - Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2)
DTC P0156 - Oxygen Sensor Circuit Malfunction (Bank 2 Sensor 2)
DTC P0157 - Oxygen Sensor Circuit Low Voltage (Bank 2 Sensor 2)
DTC P0158 - Oxygen Sensor Circuit High Voltage (Bank 2 Sensor 2)
DESCRIPTION
HINT: 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), 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 gas is rich. The HO2 sensor informs the ECM that the post-TWC air-fuel 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.
MONITOR DESCRIPTION
1. Active Air-Fuel Ratio Control
The ECM usually performs air-fuel ratio feedback control so that the Air-Fuel Ratio (A/F) 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 (TWC) and Heated Oxygen (HO2) sensor malfunctions (refer to the diagram below).
Active air-fuel ratio control is performed for approximately 15 to 20 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, one of the following DTCs is set: DTC P0136 or P0156 (abnormal voltage output), P0137 or P0157 (open circuit) or P0138 or P0158 (short circuit).
2. Abnormal Voltage Output of HO2 Sensor (DTCs P0136 and P0156)
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 HO2 sensor voltage does not decrease to less than 0.21 V or does not increase to more than 0.59 V during active air-fuel ratio control, the ECM determines that the sensor voltage output is abnormal and sets DTCs P0136 and P0156.
3. Open or Short in Heated Oxygen (HO2) Sensor Circuit (DTCs P0137 and P0157 or P0138 and P0158)
During active air-fuel ratio control, the ECM calculates the Oxygen Storage Capacity (OSC)* of the Three-Way Catalytic Converter (TWC) by forcibly regulating the air-fuel ratio to become rich or lean.
If the HO2 sensor has an open or short, or the voltage output of the sensor noticeably decreases, the OSC indicates an extraordinarily high value. Even if the ECM attempts to continue regulating the air-fuel ratio to become rich or lean, the HO2 sensor output does not change.
While performing active air-fuel ratio control, when the target air-fuel ratio is rich and the HO2 sensor voltage output is 0.21 V or less (lean), the ECM interprets this as an abnormally low sensor output voltage and sets DTC P0137 or P0157. When the target air-fuel ratio is lean and the voltage output is 0.59 V or more (rich) during active air-fuel ratio control, the ECM determines that the sensor voltage output is abnormally high, and sets DTC P0138 or P0158.
HINT: DTC P0138 or P0158 is also set if the HO2 sensor voltage output is more than 1.2 V for 10 seconds or more.
*: The TWC has the capability to store oxygen. The OSC and the emission purification capacity of the TWC are mutually related. The ECM determines whether the catalyst has deteriorated, based on the calculated OSC value P0420.
4. High or Low Impedance of Heated Oxygen (HO2) Sensor (DTCs P0136 and P0156 or P0137 and P0157)
During normal air-fuel ratio feedback control, there are small variations in the exhaust gas oxygen concentration. In order to continuously monitor the slight variation of the HO2 sensor signal while the engine is running, the impedance* of the sensor is measured by the ECM. The ECM determines that there is a malfunction in the sensor when the measured impedance deviates from the standard range.
*: The effective resistance in an alternating current electrical circuit.
- The impedance cannot be measured using an ohmmeter.
- DTCs P0136 and P0156 indicate the deterioration of the HO2 sensor. The ECM sets the DTCs by calculating the impedance of the sensor when the typical enabling conditions are satisfied (2 driving cycles).
- DTCs P0137 and P0157 indicate an open or short circuit in the HO2 sensor (2 driving cycles). The ECM sets the DTCs when the impedance of the sensor exceeds the threshold 15 kOhms.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
All:
Heated Oxygen Sensor Output Voltage (Output Voltage, High Voltage and Low Voltage):
Heated Oxygen Sensor Impedance (Low):
Heated Oxygen Sensor Impedance (High):
Heated Oxygen Sensor Output Voltage (Extremely High):
TYPICAL MALFUNCTION THRESHOLDS
Heated Oxygen Sensor Output Voltage (Output voltage):
Heated Oxygen Sensor Output Voltage (Low output voltage):
Heated Oxygen Sensor Output Voltage (High output voltage):
Heated Oxygen Sensor Impedance (Low):
Heated Oxygen Sensor Impedance (High):
Heated Oxygen Sensor Output Voltage (Extremely High):
COMPONENT OPERATING RANGE
MONITOR RESULT
Refer to CHECKING MONITOR STATUS Mode 6 Data.
WIRING DIAGRAM
CONFIRMATION DRIVING PATTERN
HINT:
- 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 (HO2) sensor monitor. (The catalyst monitor is performed simultaneously.) This is very useful for verifying the completion of a repair.
NOTE:
This test will not be completed if the vehicle is driven under absolutely constant speed conditions such as with cruise control activated.
- (a) Connect the Techstream to the DLC3.
- (b) Turn the engine switch on (IG).
- (c) Turn the Techstream ON.
- (d) Clear DTCs DTC Check / Clear.
- (e) Enter the following menus: Powertrain / Engine / Monitor.
- (f) Check that O2 Sensor / Status2 is Incomplete.
- (g) Start the engine and warm it up.
- (h) Drive the vehicle at between 40 mph and 70 mph (64 km/h and 113 km/h) for at least 10 minutes.
- (i) Those items will change to Complete as O2 Sensor / Status2 monitor operates.
- (j) Enter the following menus: Powertrain / Engine / Trouble Codes / Pending; then check if any DTCs (any pending DTCs) are set.
HINT: If O2 Sensor / Status2 does not change to Complete, and any pending DTCs fail to set, extend the driving time.
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 Techstream.
1 Connect the Techstream to the DLC3.
2 Start the engine and turn the Techstream ON.
3 Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
4 On the Techstream, enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F sensor.
5 Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume.)
6 Monitor the output voltages of the A/F and HO2 sensors (AFS Voltage B1 S1 and O2S B1 S2 or AFS Voltage B2 S1 and O2S B2 S2) displayed on the Techstream.
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 and decreases in the fuel injection volume.
NOTE:
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.
- 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: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1 S1 and O2S B1 S2 or AFS Voltage 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 Techstream. Freeze frame data records the engine condition when malfunctions are detected. 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.
- 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.
PROCEDURE
1. READ DTC OUTPUT
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream ON.
(c) Enter the following menus: Powertrain / Engine / Trouble Codes.
(d) Read DTCs.
Result:
C -- READ VALUE USING TECHSTREAM (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR)
B -- CHECK EXHAUST GAS LEAK
A -- Continue to next step.
2. READ VALUE USING TECHSTREAM (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream ON.
(c) Enter the following menus: Powertrain / Engine / Data List / A/F Control System / O2S B1 S2 or O2S B2 S2.
(d) Allow the engine to idle.
(e) Read the Heated Oxygen (HO2) sensor output voltage while idling.
Result:
B -- CHECK AIR FUEL RATIO SENSOR CURRENT
A -- Continue to next step.
3. INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)
(a) Disconnect the L50, L49 or E55 HO2 sensor connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:
Result
C -- REPLACE HEATED OXYGEN SENSOR
B -- REPLACE HEATED OXYGEN SENSOR
A -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)
(a) Turn the engine switch off and wait for 5 minutes.
(b) Disconnect the A13 ECM connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard resistance:
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM
5. CHECK AIR FUEL RATIO SENSOR CURRENT
HINT: This A/F sensor test is to check the A/F sensor current during the fuel-cut. When the sensor is normal, the sensor current will indicate below 3 mA in this test.
(a) Clear DTC DTC Check / Clear.
(b) Drive the vehicle by the drive pattern as listed below:
(1) Warm up the engine.
(2) Drive the vehicle at 40 mph (60 km/h) or more for 10 minutes or more.
(3) Stop the vehicle.
(4) Accelerate the vehicle until 40 mph (60 km/h) or more and decelerate for 3 seconds or more. Perform this three times.
(c) Enter the following menus: Powertrain / Engine / Monitor / O2 Sensor / Details.
(d) Confirm that RANGE B1S1 or RANGE B2S1 is either Pass or Fail.
(e) Select RANGE B1S1 or RANGE B2S1.
(f) Read the value.
Standard:
Less than 3.0 mA
NOTE:
Do not turn the engine switch off during this step because the test results will be lost.
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- PERFORM CONFIRMATION DRIVING PATTERN
6. READ VALUE USING TECHSTREAM (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR)
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the Techstream ON.
(c) Start the engine.
(d) Enter the following menus: Powertrain / Engine / Data List / A/F Control System / O2S B1 S2 or O2S B2 S2.
(e) After warming up the engine, run the engine at an engine speed of 2500 rpm for 3 minutes.
(f) Read the output voltage of the HO2 sensor when the engine rpm is suddenly increased.
HINT: Quickly accelerate the engine to 4000 rpm 3 times using the accelerator pedal.
Standard:
Fluctuates between 0.4 V or less and 0.5 V or more.
NG -- CHECK EXHAUST GAS LEAK
OK -- Continue to next step.
7. PERFORM ACTIVE TEST USING TECHSTREAM (INJECTION VOLUME)
(a) Connect the Techstream to the DLC3.
(b) Start the engine and turn the Techstream ON.
(c) Warm up the engine.
(d) Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume.
(e) Change the fuel injection volume using the Techstream, and monitor the voltage output of Air-Fuel Ratio (A/F) and HO2 sensors displayed on the Techstream.
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 Voltage B1 S1 or AFS Voltage B2 S1, and the HO2 sensor is displayed as O2S B1 S2 or O2S B2 S2 on the Techstream.
Result:
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.
C -- REPLACE AIR FUEL RATIO SENSOR
B -- REPLACE AIR FUEL RATIO SENSOR
A -- CHECK EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO AND REPAIR CAUSE (INJECTOR, FUEL PRESSURE, GAS LEAKAGE FROM EXHAUST SYSTEM, ETC.)
8. CHECK EXHAUST GAS LEAK
(a) Check for exhaust gas leakage from the exhaust manifold and pipe.
OK:
No gas leakage.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT
OK -- Continue to next step.
9. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
(a) Inspect heated oxygen sensor.
HINT:
- for 2WD .
- for AWD Heated Oxygen Sensor.
Result
C -- REPLACE HEATED OXYGEN SENSOR
B -- REPLACE HEATED OXYGEN SENSOR
A -- Continue to next step.
10. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)
(a) Disconnect the L50, L49 or E55 HO2 sensor connector.
(b) Turn the engine switch on (IG).
(c) Measure the voltage according to the value(s) in the table below.
Standard voltage:
(d) Turn the engine switch off.
(e) Disconnect the A13 and E1 ECM connectors.
(f) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):
Standard resistance (Check for short):
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
11. REPLACE HEATED OXYGEN SENSOR
(a) Replace the heated oxygen sensor.
HINT:
- for 2WD Removal.
- for AWD Removal.
NEXT -- Continue to next step.
12. PERFORM CONFIRMATION DRIVING PATTERN
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Clear the DTCs.
(d) Switch ECM from normal mode to check mode using the Techstream.
(e) Warm-up the engine until the engine coolant temperature is 75°C (167°F) or more.
(f) Drive the vehicle at 40 to 75 mph (60 to 120 km/h) for at 10 minutes.
(g) Drive the vehicle at 40 mph (60 km/h) or more and decelerate the vehicle for 5 seconds or more. Perform this 3 times.
(h) Turn the Techstream ON.
(i) Enter the following menus: Powertrain / Engine / Utility / All Readiness.
(j) Input DTCs: P0136, P0137, P0138, P0156, P0157 and P0158.
(k) Check that DTC monitor is NORMAL. If DTC monitor is INCOMPLETE, Perform the drive pattern adding the vehicle speed and using the second gear to decelerate the vehicle.
Result
C -- REPLACE HEATED OXYGEN SENSOR
B -- REPLACE HEATED OXYGEN SENSOR
A -- END
13. REPLACE AIR FUEL RATIO SENSOR
(a) Replace the air fuel ratio sensor.
HINT:
- for 2WD Removal.
- for AWD Removal.
NEXT -- Continue to next step.
14. PERFORM CONFIRMATION DRIVING PATTERN
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Clear the DTCs.
(d) Switch ECM from normal mode to check mode using the Techstream.
(e) Warm-up the engine until the engine coolant temperature is 75°C (167°F) or more.
(f) Drive the vehicle at 40 to 75 mph (60 to 120 km/h) for at 10 minutes.
(g) Drive the vehicle at 40 mph (60 km/h) or more and decelerate the vehicle for 5 seconds or more. Perform this 3 times.
(h) Turn the Techstream ON.
(i) Enter the following menus: Powertrain / Engine / Utility / All Readiness.
(j) Input DTCs: P0136, P0137, P0138, P0156, P0157 and P0158.
(k) Check that DTC monitor is NORMAL. If DTC monitor is INCOMPLETE, Perform the drive pattern adding the vehicle speed and using the second gear to decelerate the vehicle.
Result
C -- REPLACE HEATED OXYGEN SENSOR
B -- REPLACE HEATED OXYGEN SENSOR
A -- END