Can o2 Sensors Be Bad & Not Throw Codes?
 

We are troubleshooting some problems and speculation is bad o2 sensors.

It is argued unless it tosses a code it's ok.

True or False?

Yes yes and yes! You can have bad O2 sensors with no codes.

Old worn out O2 sensors can end up switching too slow to function right.

Over 75% of emissions tests are failed due to worn out old O2 sensors with no fault codes what so ever.

+1, you have to get some form of a scanner or scanning software on there to monitor O2 sensor activity...if the O2 sensors aren't switching rapidly, or aren't reading voltages that range from 0 to .9 volts, you have an O2 sensor problem...

Here Is a Scan
 

Attached a scan of some normal driving.

what do you think of the o2 readings? Normal?


I see some kr but it must be all apart of GM's stock tuning I guess.