Part 1
2GR-FXE ENGINE CONTROL: SFI SYSTEM: P0136-P0139,P0156-P0159: 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 P0139 - Oxygen Sensor Circuit Slow Response (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)
DTC P0159 - Oxygen Sensor Circuit Slow Response (Bank 2 Sensor 2)
CAUTION / NOTICE / HINT
DESCRIPTION
A three-way catalytic converter is used in order to convert the carbon monoxide (CO), hydrocarbon (HC), and oxides of nitrogen (NOx) into less harmful substances. To allow the three-way catalytic converter to function effectively, it is necessary to keep the air fuel ratio of the engine near the stoichiometric air fuel ratio. For 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 becomes rich. The heated oxygen sensor informs the ECM that the post-three-way catalytic converter 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 heated oxygen sensor informs the ECM that the post-three-way catalytic converter air fuel ratio is rich (high voltage, i.e. more 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 time 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.
MONITOR DESCRIPTION
1. 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 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.
2. Abnormal Voltage Output of Heated Oxygen 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 heated oxygen sensor voltage 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 or P0156.
3. Open in Heated Oxygen Sensor Circuit (DTCs P0137 and P0157)
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 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 0.21 V or less (lean), the ECM interprets this as an abnormally low sensor output voltage and sets DTC P0137 or P0157.
*: 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 P0420.
4. High or Low Impedance of Heated Oxygen 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 heated oxygen 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 or P0156 indicates the deterioration of the heated oxygen sensor. The ECM sets the DTCs by calculating the impedance of the sensor when the typical enabling conditions are satisfied (2 driving cycles).
- DTC P0137 or P0157 indicates an open or short circuit in the heated oxygen sensor (2 driving cycles). The ECM sets the DTCs when the impedance of the sensor exceeds the threshold 15 kOhms.
5. Extremely High Output Voltage of Heated Oxygen Sensor (DTC P0138 and P0158)
The ECM continuously monitors the heated oxygen sensor output voltage while the engine is running.
DTC P0138 or P0158 is stored if the heated oxygen sensor voltage output is more than 1.2 V for 10 seconds or more.
6. Heated Oxygen Sensor Voltage Fuel Cut (DTC P0139 and P0159)
The sensor output voltage drops to below 0.2 V (extremely lean status) immediately when the vehicle decelerates and fuel cut is operating. If the voltage does not drop to below 0.2 V for 6 seconds or more, or voltage does not drop from 0.35 V to 0.2 V for 1 second the ECM determines that the sensor's response has deteriorated, illuminates the MIL and sets a DTC.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
All
Heated Oxygen Sensor Output Voltage (Output Voltage and Low Voltage)
Heated Oxygen Sensor Low Impedance
Heated Oxygen Sensor High Impedance
Heated Oxygen Sensor Output Voltage (Extremely high)
Heated Oxygen Sensor Voltage During Fuel Cut
TYPICAL MALFUNCTION THRESHOLDS
Heated Oxygen Sensor Output Voltage (Output Voltage)
Heated Oxygen Sensor Output Voltage (Low Output Voltage)
Heated Oxygen Sensor Low Impedance
Heated Oxygen Sensor High Impedance
Heated Oxygen Sensor Output Voltage (Extremely High)
Heated Oxygen Sensor Voltage During Fuel Cut
COMPONENT OPERATING RANGE
MONITOR RESULT
Refer to Checking Monitor Status Mode 6 Data.
CONFIRMATION DRIVING PATTERN
P0136, P0137, P0138, P0156, P0157 and P0158:
1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG) and turn the Techstream to on.
3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
4. Turn the power switch off and wait for 30 seconds.
5. Turn the power switch on (IG) and turn the Techstream on [A].
6. Put the engine in inspection mode Component Tests and General Diagnostics.
7. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher [B].
8. Drive the vehicle at 37 to 75 mph (60 to 120 km/h) for 10 minutes or more [C].
9. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.
10. Read the pending DTC [D].
HINT
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
11. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
12. Input the DTC: P0136, P0137, P0138, P0156, P0157, or P0158.
13. Check the DTC judgment result.
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
HINT
- 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 UNKNOWN, perform steps [C] again.
14. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
15. Input the DTC: P0136, P0137. P0138, P0156, P0157 or P0158.
16. Check the DTC judgment result.
HINT
- If the judgment result shows NORMAL, the system is normal.
- If the judgment result shows ABNORMAL, the system has a malfunction.
17. If the test result is INCOMPLETE or UNKNOWN and no pending DTC is output, perform a universal trip and check for permanent DTCs Reading and Clearing Diagnostic Trouble Codes.
HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.
P0139 and P0159:
1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG) and turn the Techstream on.