Wondering if any of these issues are related. I have a 2012 TL with 185K. Love the car and it’s been virtually problem free until now. First, the noise….I thought I had a flat spot on my tire. Purchase new tire and the rhythmic thump is still there. Rhythm increases as the speed increases. Next, the car threw a P0430 code….downstream O2 sensor. Next, I noticed oil on my garage floor. I slid under the car to have a look. It looks like there is oil coming from between the tranny and the engine. Main seal? PCV valve? I don’t think these are related but thought I pose the questions to the experts.

 

do you have an AWD TL or Front-Wheel Drive (FWD). When is the last time you did the timing belt service?

You should start looking for leaks that start up top on the engine and can work down. For example the rear valve cover gasket can leak and drip down near the Rear main seal - Clean off all impacted areas and inspect.

If it looks like rear main seal, it could be a rubber bit that sits on the plate that the RMS goes into (top of the plate, requires removal of plate that holds RMS). You might be able to fix it with a new PCV if the old one is pressurizing the crankcase too much.

If you have AWD - is your car burning oil? If yes, oil burning can degrade the cat's and cause issues. Also common issue to damage the rear camshaft and that can cause a noise. Also check belt tensioner for accessory belt and make sure it's not the cause of sound.

Either way, You can try a product like catacleen from auto-parts store, follow directions and it might eliminate the code. Best thing to do is use a scan tool to see live data to make sure it's actually functioning and not stuck at a random value (sensor failure).

 

Rhythmic thump - How are the suspension components up front? AWD or FWD?

CEL - Replace the O2, a lot cheaper than a new cat.

Leak - Probably rear main seal, I've got an ever so slight leak coming from mine and it'll be on the list to tackle at some point.