Description

The A/F sensor generates a voltage that corresponds to the actual air-fuel ratio. This sensor voltage is used to provide the ECM with feedback so that it can control the air-fuel ratio. The ECM determines the deviation from the stoichiometric air-fuel ratio level, and regulates the fuel injection time. If the A/F sensor malfunctions, the ECM is unable to control the air-fuel ratio accurately.

The A/F sensor is the planar type and is integrated with the heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte though the alumina, therefore the sensor activation is accelerated.

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 level.

: Value changes inside the ECM. Since the A/F sensor is the current output element, a current is converted in to a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.

Element

Exhaust Gas n

Cover

Alumina

Heater

Solid Electrolyte (Zirconia Element)

ECM Monitored A/F Sensor Voltage

Platinum Electrode Atmospheric Air

12 13 14 15 16 17 18

Air Fuel Ratio

A-A Section

A107164E08

A107164E08

DTC No.

DTC Detection Conditions

Trouble Areas

P2195 P2197

Conditions (a) and (b) continue for 10 seconds or more (2 trip detection logic)

(a) Air-Fuel Ratio (A/F) sensor voltage more than 3.8 V

(b) Heated Oxygen (HO2) sensor voltage 0.15 V or more

• Open or short in A/F sensor (bank 1, 2 sensor 1) circuit

• A/F sensor heater relay

• A/F sensor heater and relay circuits

• Air induction system

• Fuel pressure

• ECM

P2195 P2197

While fuel-cut operation performed (during vehicle deceleration), air-furl ratio (A/F) sensor current 3.6 mA or more for 3 seconds (2 trip detection logic)

• ECM

P2196 P2198

Conditions (a) and (b) continue for 10 seconds or more (2 trip detection logic)

(a) A/F sensor voltage less than 2.8 V

(b) HO2 sensor voltage less than 0.6 V

• Open or short in A/F sensor (bank 1, 2 sensor 1) circuit

• A/F sensor heater relay

• A/F sensor heater and relay circuits

• Air induction system

• Fuel pressure

• ECM

P2196 P2198

While fuel-cut operation performed (during vehicle deceleration), air-furl ratio (A/F) sensor current less than 1.57 mA for 3 seconds (2 trip detection logic)

• DTCs P2195 and P2196 indicate malfunctions related to bank 1 A/F sensor circuit.

• DTCs P2197 and P2198 indicate malfunctions related to bank 2 A/F sensor circuit.

• Bank 1 refers to the bank that includes cylinder No. 1.

• Bank 2 refers to the bank that includes cylinder No. 2.

• When any of these DTCs are set, check the A/F sensor voltage output by selecting the following menu items on an intelligent tester: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / AFS B1S1 or AFS B2S1.

• Short-term fuel trim values can also be read using an intelligent tester.

• The ECM regulates the voltages at the A1A+, A2A+, A1A- and A2A- terminals of the ECM to a constant level. Therefore, the A/F sensor voltage output cannot be confirmed without using an intelligent tester.

• If a A/F sensor malfunction is detected, the ECM sets a DTC.

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