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 sensor is used.

The heated oxygen 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 high. The heated oxygen 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 is low. The heated oxygen sensor informs the ECM that the post-TWC 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 TWC 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.

2.979,1.229 3.292,0.844 false 2.688,1.792 3.302,1.792 true 2.583,2.417 3.24,2.385 true 2.677,2.719 3.26,2.854 false 1.094,2.917 1.333,2.917 false 2.667,1.458 2.667,1.531 false 2.781,1.469 3.219,1.26 3.219,1.26 2.656,1.385 true 2.146,0.635 3.292,0.958 1.146,0.323 10 false Atmosphere 3.344,0.74 4.083,0.938 0.74,0.198 10 false Housing 3.281,1.188 4.698,1.458 1.417,0.271 10 false Platinum Electrode 4.208,0.771 5.198,1.052 0.99,0.281 10 false Output Voltage 5.208,0.958 6.604,1.292 1.396,0.333 10 false Ideal Air Fuel Mixture 2.01,3.167 2.948,3.5 0.938,0.333 10 false Exhaust Gas 3.344,1.698 4.688,2.146 1.344,0.448 10 false Solid Electrolyte (Zirconia Element) 3.302,2.792 4.521,3.188 1.219,0.396 10 false Coating (Ceramic) 3.323,2.313 3.854,2.615 0.531,0.302 10 false Heater 1.365,2.833 1.885,3.167 0.521,0.333 10 false Cover 4.792,2.896 7.042,3.281 2.25,0.385 10 false Richer - Air Fuel Ratio - Leaner

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 (TWC) 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, this DTC is stored.

Open in Heated Oxygen Sensor Circuit

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 heated oxygen sensor has an open or short circuit, or the voltage output of the sensor noticeably decreases, the OSC indicates an extremely 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 less than 0.21 V (lean), the ECM interprets this as an abnormally low sensor output voltage and stores DTC P0137.

*: 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.

5.813,3.792 6.021,4.052 false 4.292,2.052 4.448,1.76 false 4.448,1.76 4.594,1.76 false 5.344,2.396 5.479,1.75 5.479,1.75 5.635,1.75 true 5.698,3.01 5.844,2.583 false 5.844,2.583 6,2.583 false 0.063,0.042 4.563,0.25 4.5,0.208 10 false Heated Oxygen Sensor Circuit Low Voltage (Open) 0.281,1.292 2.698,1.5 2.417,0.208 10 false Active Air Fuel Ratio Control 0.281,3.292 3.083,3.5 2.802,0.208 10 false Heated Oxygen Sensor Voltage 0.281,2.073 2.281,2.26 2,0.188 10 false Target Air Fuel Ratio 2.083,2.073 2.979,2.427 0.896,0.354 10 false Stoichiometric Air Fuel Level 2.76,1.385 3.125,1.583 0.365,0.198 10 false OFF 2.49,3.552 2.979,3.75 0.49,0.198 10 false 0.21 V 4.281,0.74 5.365,1.104 1.083,0.365 10 false Approximately 30 seconds 4.521,1.302 5.281,1.5 0.76,0.198 10 false Operation 4.656,1.667 5.219,1.865 0.563,0.198 10 false Normal 5.688,1.667 6.333,1.865 0.646,0.198 10 false Abnormal 6.063,4.083 6.802,4.281 0.74,0.198 10 false Abnormal 6.052,2.5 6.615,2.698 0.563,0.198 10 false Normal 4.781,2.438 5.146,2.635 0.365,0.198 10 false Rich

HINT:

·

This confirmation driving pattern is used in the "Perform Confirmation Driving Pattern" procedure of the following diagnostic troubleshooting procedure.

·

Performing this confirmation pattern will activate the heated oxygen sensor monitor (the catalyst monitor is performed simultaneously). This is very useful for verifying the completion of the repair.

1.74,2.427 1.563,2.802 1.563,2.802 1.417,2.802 false 4.021,0.719 4.25,0.958 0.229,0.24 10 [C] 3.49,2.906 4.792,3.083 1.302,0.177 10 10 minutes or more 1.094,1.354 1.698,1.51 0.604,0.156 10 60 km/h 2.021,2.427 2.25,2.625 0.229,0.198 10 [A] 1.021,0.479 1.677,0.688 0.656,0.208 10 100 km/h 1.25,2.229 1.635,2.448 0.385,0.219 10 Idling 0.229,2.74 1.49,2.958 1.26,0.219 10 Ignition Switch ON 2.677,2.135 2.906,2.344 0.229,0.208 10 [B] 2.333,2.917 3.156,3.115 0.823,0.198 10 Warming up 5.01,3.313 5.271,3.573 0.26,0.26 10 [D]

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 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 GTS.

1.

Connect the GTS to the DLC3.

2.

Start the engine.

3.

Turn the GTS on.

4.

Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

5.

Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / All Data / AFS Voltage B1S1 and O2S B1S2.

6.

Perform the Active Test operation with the engine idling (change the fuel injection volume).

7.

Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the GTS.

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 12.5%.

·

Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

Standard:

GTS 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

NOTICE:

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.

5.792,3.781 7.115,4.052 1.323,0.271 10 - Air fuel ratio sensor 3.823,4.927 4.531,5.104 0.708,0.177 8 Below 0.4 V 3.208,4.396 4.333,4.615 1.125,0.219 10 Output Voltage 3.25,3.365 4.542,3.615 1.292,0.25 10 Injection Volume 3.229,1.292 4.521,1.542 1.292,0.25 10 Injection Volume 3.24,2.313 4.333,2.521 1.094,0.208 10 Output Voltage 0.625,1.292 1.917,1.542 1.292,0.25 10 Injection Volume 0.625,3.365 1.917,3.615 1.292,0.25 10 Injection Volume 0.594,5.438 1.885,5.688 1.292,0.25 10 Injection Volume 0.604,7.49 1.896,7.74 1.292,0.25 10 Injection Volume 3.25,7.49 4.542,7.74 1.292,0.25 10 Injection Volume 3.25,5.438 4.542,5.688 1.292,0.25 10 Injection Volume 0.635,2.302 1.823,2.51 1.188,0.208 10 Output Voltage 0.625,4.396 1.792,4.646 1.167,0.25 10 Output Voltage 0.552,6.479 1.719,6.729 1.167,0.25 10 Output Voltage 0.573,8.563 1.74,8.813 1.167,0.25 10 Output Voltage 3.24,8.563 4.406,8.813 1.167,0.25 10 Output Voltage 3.25,6.479 4.417,6.729 1.167,0.25 10 Output Voltage 3.51,4.698 4.542,4.885 1.031,0.188 8 Higher than 0.55 V 0.927,2.646 1.958,2.833 1.031,0.188 8 Higher than 3.4 V 1.177,2.885 1.927,3.073 0.75,0.188 8 Below 3.1 V 1.531,1.594 1.979,1.781 0.448,0.188 8 12.5% 1.479,1.833 1.927,2.021 0.448,0.188 8 -12.5% 3.5,2.604 4.531,2.792 1.031,0.188 8 Higher than 0.55 V 3.813,2.844 4.521,3.021 0.708,0.177 8 Below 0.4 V 4.156,1.594 4.604,1.781 0.448,0.188 8 12.5% 4.115,1.833 4.563,2.021 0.448,0.188 8 -12.5% 4.146,3.729 4.594,3.917 0.448,0.188 8 12.5% 4.104,3.917 4.552,4.104 0.448,0.188 8 -12.5% 4.104,5.958 4.552,6.146 0.448,0.188 8 -12.5% 4.104,8.021 4.552,8.208 0.448,0.188 8 -12.5% 4.156,5.74 4.604,5.927 0.448,0.188 8 12.5% 4.156,7.813 4.604,8 0.448,0.188 8 12.5% 1.49,7.813 1.938,8 0.448,0.188 8 12.5% 1.49,5.75 1.938,5.938 0.448,0.188 8 12.5% 1.5,3.677 1.948,3.865 0.448,0.188 8 12.5% 1.448,3.896 1.896,4.083 0.448,0.188 8 -12.5% 1.448,5.948 1.896,6.135 0.448,0.188 8 -12.5% 1.438,8.021 1.885,8.208 0.448,0.188 8 -12.5% 0.844,4.802 2.042,5.052 1.198,0.25 8 Almost no reaction 0.854,8.938 2.052,9.188 1.198,0.25 8 Almost no reaction 3.5,8.938 4.698,9.188 1.198,0.25 8 Almost no reaction 3.49,6.865 4.688,7.115 1.198,0.25 8 Almost no reaction 0.917,6.771 1.948,6.958 1.031,0.188 8 Higher than 3.4 V 1.167,7.021 1.917,7.208 0.75,0.188 8 Below 3.1 V 0.24,2.083 0.396,2.281 0.156,0.198 10 1 0.24,4.25 0.396,4.448 0.156,0.198 10 2 0.25,6.333 0.406,6.531 0.156,0.198 10 3 0.24,8.417 0.396,8.615 0.156,0.198 10 4 0.125,0.688 0.573,0.938 0.448,0.25 10 Case 0.792,0.583 2.802,0.969 2.01,0.385 10 Air Fuel Ratio Sensor (Sensor 1) Output Voltage 3.5,0.583 5.594,1.031 2.094,0.448 10 Heated Oxygen Sensor (Sensor 2) Output Voltage 5.969,0.583 7.01,1 1.042,0.417 10 Main Suspected Trouble Area 6.396,2.115 6.552,2.313 0.156,0.198 10 - 5.802,4.031 7.125,4.469 1.323,0.438 10 - Air fuel ratio sensor heater 5.802,4.448 7.125,4.885 1.323,0.438 10 - Air fuel ratio sensor circuit 5.917,5.792 6.969,6.167 1.052,0.375 10 - Heated oxygen sensor 5.927,6.198 6.969,6.625 1.042,0.427 10 - Heated oxygen sensor heater 5.927,6.615 6.969,7.052 1.042,0.438 10 - Heated oxygen sensor circuit 5.927,7.698 6.813,8.104 0.885,0.406 10 - Fuel injector assembly 5.917,8.115 7.073,8.448 1.156,0.333 10 - Fuel pressure 5.917,8.365 6.969,9.375 1.052,1.01 10 - Gas leak from exhaust system (air fuel ratio extremely rich or lean) 2.552,2.75 3,2.938 0.448,0.188 8 OK 2.5,4.719 2.948,4.906 0.448,0.188 8 NG 2.552,6.865 3,7.052 0.448,0.188 8 OK 2.5,8.844 2.948,9.031 0.448,0.188 8 NG 5.167,2.708 5.615,2.896 0.448,0.188 8 OK 5.167,4.813 5.615,5 0.448,0.188 8 OK 5.135,8.854 5.583,9.042 0.448,0.188 8 NG 5.135,6.771 5.583,6.958 0.448,0.188 8 NG

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.

HINT:

·

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 GTS. 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.