How likely would a catalytic converter fail?

[chensyd]

Hi all. I've been monitoring my 2009 Aurion ATX (GSV40) for some time after the fuel consumption degraded from 10-11L/100km to 15-16L/100km in urban condition with half time on highway.

With 150K on odometer.

I recently changed new spark plugs, cleaned MAF sensor, throttle body and the pre-cat oxygen sensor in the front.

I used ODB scanner tool to monitor several sensors

• Pre-cat sensor voltage and mixture ratio
• Post-cat voltage
• Throttle position

The findings are

• Both pre-cat sensors stay around 3.3v
• Post-cat voltage fluctuate between 0 to 0.8v. I attached the graph below along with throttle position.

From this post https://mechanics.stackexchange.com/questions/50101/02-sensor-displays-constant-3-3-volts-not-a-jagged-waveform-2002-rav4
 

Quote

The rear sensors are standard oxygen sensors. These readings, with the swings up and down from .2 to .8 volts, are indicative of failed catalysts. Good catalysts would be showing steady voltage readings.

It appears my post-cat sensor reading may indicate a failed catalysts? There is no check engine light come up.

I'm wondering how likely the cat converter is going to fail?

Some symptoms I can relate to is the car always have strong fume smell when start in the morning, but back to normal after warm up.

Any ideas are appreciated.