A/F Sensor Current Inspection

Warm up the engine to normal operating temperature.
Using the M-MDS, monitor the following:
- Vehicle speed (PID: VSS)
- Engine speed (PID: RPM)
- A/F sensor current (PID: O2S11)
Drive the vehicle and decelerate the engine speed by releasing the accelerator pedal fully when the engine speed is 3,000 rpm or more.
Verify that the A/F sensor current (PID: O2S11) is 0.25 mA or more while decelerating as shown in the figure.

Fig 1: Front Heated Oxygen Sensor Current Graph
Courtesy of MAZDA MOTORS CORP.
- If not within the specification, inspect the HO2S for an open or short circuit. (See A/F sensor CIRCUIT OPEN/SHORT INSPECTION (SENSOR) .) Then if there is no malfunction in the wiring harness, replace the A/F sensor.