My 2008 infiniti g35x, 180000 miles, has codes p0420 and p0011, my scan tool shows both upstream 02 sensors reading .02-.05 and both down stream 02 sensors reading 2.2-2.5. my scan tool shows the catalytic converter temperatures not moving up at idle and even in some cases it shows the temperature going down. But when I use an infrared laser to check the temperature the cats are operating normal where the outlet shows hotter than the inlet. I got no driveability issues or rough idle, my short term fuel trim is around -7. My catalytic converters are rattling. Where should I start with this issue and are those numbers correct for the 02 sensor readings?
are those numbers correct for the 02 sensor readings?
Your upstream sensor output will depend on whether it is an old-school narrow-band sensor or the newer type wide-band sensor which is actually an air/fuel ratio sensor.
The former typically varies between 0 and 1 volt during normal operation, the latter just shows a reference voltage and varies current to indicate the air/fuel ratio to the computer. Downstream sensors should show a relatively constant voltage with small variations.
My catalytic converters are rattling
Then they're most likely breaking up inside unless it's just the heat shields rattling.
Where should I start with this issue
Consulting a repair manual might be a good place to start:
https://charm.li/Infiniti/2008/G35x%20Sedan%20AWD%20V6-3.5L%20%28VQ35HR%29/
Follow these troubleshooting steps the service manual:
P0011
P0420
My catalytic converters are rattling.
If the rattle is inside , and not from rusted/broken exhaust clamps/hangers etc, then mostly likely they've collapsed and need to be replaced.
