Joe ZHONG

4 minutes ago, steve2006 said:

The IS engine is a straight six cylinder so only one O2 sensor is used, hence bank 2 not being used.

You also say the sensor is working well....how have you confirmed this?..the only way to confirm switching is to use an oscilloscope to check the sensor output waveform for correct amplitude, duty cycle and frequency. also confirm the heater supply is present.

If you have access to real time diagnostics you should be able to see the fuel trim figures.

Main causes of failed cats are an over rich fuel mixture allowing unburnt fuel to enter the cat and a misfire which will do the same.

Is the ignition servicing up to date with air filter and spark plugs?

Coil packs often fail on this engine so check all six are functioning correctly but they normally flag up a code if failure is detected.

Nearly forgot....welcome to the LOC.

Hi Steve,

Thanks for your reply. Cannot believe I forgot to mention the model. It is actually GS300, not IS.

The sensors on bank 1 are okay because:

sensor 1's voltage is around 0.5 and sensor 2's is around 0.1, so I thought they were good.

I didn't understand the fuel trim figures, but I will do some research and try to read them again.

My car had a main service in Jan 2016, but I am not sure whether they check ignitions or not. I presume they check and replace filters.

Have you got some more ideas please?

Thank you.

Model GS300 2005-2011

Got 3 lights on my dashboard. I have replaced the rear oxygen sensors.

The code is showing that catalytic converter on bank 2 needs to be replaced, and one of my friends in a garage told me so as well.

However, he didn't tell me what caused the problem. As people say, I need to find out the real problem before I replace the CAT.

I took some real-time readings from my OBD reader, and found sensors on bank 1 perfectly normal (of course), and sensors on bank 2 showing "not used"

As far as I knew, the O2s will not be used in open loop. However, the fuel system status is closed loop, which means O2 sensors are being used. And also sensors on bank 1 are working well.

Then on wiki, I found this: (if B==$FF, sensor is not used in trim calculation).

This is not for the O2 voltage, but the short term fuel trim calculation formula.

The $FF stands for the maximum possible value. So does this mean all 2 oxygen sensors are working at full capacity? What does this mean?

Could anybody help me find the true cause of the problem please?

Thanks.