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2001 Saturn L-Series 3.0L with P0030 and P0050 Codes: Poor Running, Bogging, and O2 Heater Issues

Model: 2001 Saturn L-series Fault Code: P0030 Posted: 2015-01-14 19:17

My 2001 Saturn L-Series 3.0L has started running poorly with the Check Engine Light on. The vehicle displays diagnostic codes P0030 and P0050, along with random misfire codes (including P0300, P0302, and P0304). It feels like the engine is bogging down under load, especially when accelerating—O2 sensor voltage remains normal until throttle input, after which it drops sharply. The codes persist and won't clear, suggesting a deeper issue. Notably, both O2 heater circuits are failing simultaneously, which is unusual. I've checked fuses and confirmed the O2 heater fuse is good. There's also a faint rotten egg smell, possibly indicating exhaust system issues. Given that misfires can cause catalytic converter clogging, I'm concerned about potential damage to the exhaust system. Any insights on how to diagnose or fix this?

Related fault codes
P0030P0050
Comments (5)
Anonymous 2015-01-14 20:51

Could you confirm which specific skip codes you're seeing? For O2 heater issues, start by checking the fuses and wiring. A vacuum gauge can help determine if the catalytic converter is clogged or restricting exhaust flow.

Anonymous 2015-01-14 20:58

I've seen P0300, P0302, and P0304—random misfires in cylinders 2 and 4. I'm considering removing the catalytic converter to test if engine performance improves. The rotten egg smell is concerning and may point to a leak or internal issue.

Anonymous 2015-01-14 21:02

The car barely starts now and stalls when I release the throttle. When I disconnected the MAF sensor, it stalled immediately—this suggests the MAF might be faulty or contributing to misfires, though I'm not certain of its exact role.

Anonymous 2015-01-15 21:34

P0300 indicates random misfire; P0302 and P0304 point to misfires in cylinders 2 and 4. If the engine is misfiring, it can cause exhaust backpressure and overheat the catalytic converter—this may result in a red glow or complete blockage. I recommend disconnecting the catalytic converter to test if performance improves. Running with a clogged converter can lead to further damage.

Anonymous 2015-01-15 21:38

If the engine runs better after removing the catalytic converter, it confirms that misfires are causing exhaust flow restriction. In this case, you'll need to replace the catalytic converter and address the underlying misfire issues—this is also likely why the O2 heater codes (P0030/P0050) persist.