P0138
DTC P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)DTC P0138 Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2)
DTC P0139 Oxygen Sensor Circuit Slow Response (Bank 1 Sensor 2)
DTC P0156 Oxygen Sensor Circuit Malfunction (Bank 2 Sensor 2)
DTC P0158 Oxygen Sensor Circuit High Voltage (Bank 2 Sensor 2)
DTC P0159 Oxygen Sensor Circuit Slow Response (Bank 2 Sensor 2)
DESCRIPTION
DTC Detection Condition:
HINT: Sensor 2 refers to the sensor mounted behind the Three-Way Catalyst 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 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.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Conditions:
Typical Malfunction Thresholds:
Component Operating Range:
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.
MONITOR RESULT
Detailed information on Checking Monitor Status. Checking Monitor Status
The test value and test limit information are described as shown in the table. Check the monitor result and test values after performing the monitor drive pattern (refer to "Confirmation Monitor").
- MID (Monitor Identification Date) is assigned to each emission-related component.
- TID (Test Identification Date) is assigned to each emission-related component.
- Scaling is used to calculate the test value indicated on generic OBD II scan tools.
If the sensor voltage is outside the standard values, the ECM interprets this as a malfunction and sets a DTC.
CONFIRMATION DRIVING PATTERN
Confirmation Driving Pattern:
a. Connect the intelligent tester to the DLC3.
b. Switch the ECM From normal mode to check mode using the tester.
c. Start the engine and warm it up until the engine coolant temperature reaches more than 75 degrees C (167 degrees F).
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].
NOTE: 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.
HINT:
Intelligent tester only:
Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE TEST. The A/F CONTROL 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 operation using an intelligent tester.
1. Connect the intelligent tester to the DLC3.
2. Start the engine and turn the tester ON.
3. Warm up the engine at engine speed of 2,500 rpm for approximately 90 seconds.
4. On the tester, enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
5. 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).
6. 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 A/F CONTROL 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.
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 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: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2, and press the YES button and then the ENTER button followed by the F4 button.
Wiring Diagram (Part 1):
Wiring Diagram (Part 2):
Step 1-2:
Step 3-4:
Step 5-8:
Step 9-13:
Step 13(Continued):
Step 14-15:
Step 16:
Step 17:
Step 17(Continued):
INSPECTION PROCEDURE
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.