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      11-15-2021, 12:03 PM   #3
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Drives: 2009 E90 335xi, 2011 E93 M3
Join Date: Dec 2012
Location: Boston

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Originally Posted by mirracobmx40 View Post
Im throwing o2 codes pretty much every time I turn the car on, multiple times per day. My afrs were frozen during tuning so we replaced two with a set from another project and that seemed to fix it so we could tune. I have been clearing the codes and driving as normal and haven't seen or noticed any issues. Someone told me bad o2s can damage cats and cause bad fuel economy but I have catless dps and straight pipe exhaust and could care less about fuel economy.

So is it really necessary to replace bad cats? Or are these codes being thrown due to the catless downpipes? Codes attached.
Like Dave92N54 says, the code reports a bank 2, pre-cat O2 sensor heater failure. The heater is there to get the sensor up to operating temperature as quickly as possible. The sensor will eventually be warmed sufficiently by the exhaust so in theory, you don't need to address this as long as you avoid WOT until the sensors are fully operational. However, addressing the problem is the prudent course of action. And of course, is necessary to pass inspection in most if not all states

The shadow codes are caused by the absence of the catalytic converters - but you don't need to worry about those - they are only shadow codes.

Since you've already replaced the sensors once, my guess is that you don't have a problem with the sensor itself - you have a fuse, connector, ground or wiring problem.

Last edited by dpaul; 11-15-2021 at 04:30 PM..
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