Air Fuel Ratio Sensor

ON-VEHICLE INSPECTION

1. INSPECT AIR FUEL RATIO SENSOR

a. Disconnect the A/F sensor connector.




b. Measure the heater resistance between terminals 1 (HT) and 2 (+B) of the sensor.

Standard resistance: 1.8 to 3.4 Ohms at 20 degrees C (68 degrees F)

If the result is not as specified, replace the sensor.

2. INSPECT AIR-FUEL RATIO COMPENSATION SYSTEM




a. Measure the voltage between the terminals of the ECM connectors.






NOTE:
- Connect the tester leads from the backside of the connector. The connector should not be disconnected from the ECM.
- The voltage between the terminals of the ECM is kept constant regardless of the voltage of the A/F sensor.




b. Connect the intelligent tester to the DLC3.
c. Turn the engine switch on (IG).
d. Select the following menus: DIAGNOSIS / ENHANCED OBD II / DATA LIST / A/FS B1 S1, A/ FS B2 S1, O2S B1 S2 and O2S B2 S2.
e. Warm up the A/F sensor by running the engine at 2, 500 rpm for approximately 2 minutes.




f. Keep the engine speed at 2,500 rpm and confirm that the displays of "A/FS B1 S1" and "A/FS B2 S1" are as shown in the illustration.

HINT:
- The illustration may slightly differ from the display on the intelligent tester.
- The waveform of the A/F sensor is displayed only on the intelligent tester.

g. Check the displays of "O2S B1 S2" and "O2S B2 S2" with the engine speed at 2,500 rpm.

Standard condition: Displays show that each voltage fluctuates between 0 and 1 V.

NOTE:
- Perform the check immediately after warming up the engine.
- If the voltage oscillation could not be verified, warm up the heated oxygen sensor again. If it is still not possible to verify, perform DTC check.