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: View Of A/F Sensor Current Graph

Courtesy of MAZDA MOTORS CORP.

If not within the specification, inspect the A/F sensor for an open or short circuit. (See A/F SENSOR CIRCUIT OPEN/SHORT INSPECTION .) Then if there is no malfunction in the wiring harness, replace the A/F sensor. (See AIR FUEL RATIO (A/F) SENSOR REMOVAL/INSTALLATION .)