P0136
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
DTC Detection Condition:
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 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
Monitor Strategy (Part 1):
Monitor Strategy (Part 2):
Typical Enabling Conditions:
Typical Malfunction Thresholds:
Component Operating Range:
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
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, a DTC is set.
Abnormal Voltage Output of HO2 Sensor (DTC 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 and 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 DTC P0136 or P0156.
Open or Short in Heated Oxygen (HO2) Sensor Circuit (DTC 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 decreases significantly, 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.
High or Low Impedance of Heated Oxygen (HO2) Sensor (DTC P0136 and P0156 or P0137 and P157)
During normal air-fuel ratio feedback control, there are small variations in the exhaust gas oxygen concentration. In order to continuously monitor the slight variations in 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.
HINT:
- The impedance cannot be measured using an ohmmeter.
- DTC P0136 and P0156 indicate the deterioration of the HO2 sensor. The ECM sets this DTC by calculating the impedance of the sensor when the typical enabling conditions are satisfied (2 driving cycles).
- DTC P0137 and P0157 indicate an open or short circuit in the HO2 sensor (2 driving cycles). The ECM sets this DTC when the impedance of the sensor exceeds the threshold 50 kohms.
MONITOR RESULT
Refer to CHECKING MONITOR STATUS Checking Monitor Status
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.
HINT:
- .1: Intelligent tester
- .2: Techstream
1. Connect the intelligent tester or Techstream to the DLC3.
2. Turn the ignition switch ON.
3. Warm-up the engine until the engine coolant temperature is 75 °C (167 °F) or more [A].
4. Drive the vehicle at between 60 km/h and 120 km/h (40 mph and 75 mph) for at least 10 minutes [B].
5. Drive the vehicle 60 km/h (40 mph) or more and decelerate the vehicle for 5 seconds or more. Perform this 3 times [C].
6. Turn the tester ON.
7. Enter the following menus:
- Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / MONITOR INFO / ALL READINESS.
- Techstream - Select: Powertrain / Engine / Utility / All Readiness.
8. Input DTCs: P0136, P0137, P0138, P0156, P0157 and P0158.
9. Check the DTC MONITOR is PASS DTC not set. If DTC MONITOR is Unavailable, perform the drive pattern adding the vehicle speed and using the second gear to decelerate the vehicle.
Wiring Diagram:
Step 1-2:
Step 2(Continued)-4:
Step 5:
Step 5(Continued)-7:
Step 7(Continued)-8:
Step 8(Continued)-13:
Step 14-18:
Step 19:
Step 19(Continued)-21:
Step 21(Continued)-22:
Step 23:
Step 23(Continued):
INSPECTION PROCEDURE
HINT: Malfunctioning areas can be identified by performing the A/F CONTROL.1 (Control the Injection Volume for A/F sensor.2) function provided in the Active Test. The A/F CONTROL (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 A/F CONTROL (Control the Injection Volume for A/ F sensor) operation using the intelligent tester or Techstream.
*1: Intelligent tester
*2: Techstream
1. Connect the intelligent tester or Techstream to the DLC3.
2. Start the engine and turn the tester ON.
3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
4. On the tester, enter the following menus:
a. Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
b. Techstream - Select: Powertrain / Engine and ECT / 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 B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the tester.
HINT:
- The A/F CONTROL (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 A/F CONTROL or 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: (1)Intelligent tester - Select: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / A/F CONTROL SYS / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2; then press the YES button and the ENTER button followed by the F4 button. (2) Techstream - Select: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/ F Sensor / A/F Control System / 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 or 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.