Mazda 3 Service Manual: Heated Oxygen Sensor (HO2 S) Inspection [Mzr 2.0, Mzr 2.5]

HO2S Inspection

1. Connect the M-MDS to the DLC-2.

2. Switch the ignition to ON.

3. Warm up the engine to normal operating temperature.

4. Access the following PIDs using the M-MDS..

• VSS (Vehicle speed)

• RPM (Engine speed)

• O2S12 (HO2S output voltage)

5. Drive the vehicle and decelerate the engine speed by releasing the accelerator pedal fully when the engine speed is 3,000 rpm or more

.

6. Verify that the HO2S outputs a voltage of 0.6 V or more

, one time or more, then verify that the HO2S voltage (PID: O2S12) is 0.3 V or less

while decelerating as shown in the figure.

• If not as specified, replace the HO2S..

HO2S Heater Inspection

WARNING:

• A hot engine and exhaust system can cause severe burns. Turn off the engine and wait until they are cool before removing the exhaust system.

1. Remove the battery cover..

2. Disconnect the negative battery cable..

3. Disconnect the HO2S connector.

4. Measure the resistance between HO2S terminals C and D.

• If not as specified, replace the HO2S..

HO2S heater resistance

• 2—50 ohms [normal temperature]