I finally sold my F-Type R a few weeks ago. I had dropped the price several times, way below private party blue book, almost into dealer trade-in blue book territory. Quite literally on my way to take the car to the car hauler (the buyer was out of state and wanted it shipped) the car decided to go into limp mode. It had been clean of codes and problems for several weeks, after replacing the battery seemed to make all the troubles go away.

I've been going back and forth with the buyer. At first it was pedal code (which he had replaced) and o2 codes which have apparently gone away, but now a lingering P4030 remains. Buyer says o2 sensors have been inspected by both dealer and a separate shop, and that they are good. They both apparently recommend replacing the cat, $3500+ USD. Not one o2 sensor has been replaced yet, if I'm understanding the buyer correctly.

Everything in me is telling me the o2's should be replaced first before replacing a cat. Wouldn't one or more faulty o2 sensor (or some combination of them) cause the PCM to report the cat as bad? In my life and the half dozen or so vehicles I've owned, I've replaced enough o2 sensors to know those things are notorious for going bad, and not once have I ever replaced a cat on any vehicle I've owned. The only person I know who has ever replaced one was my mom, who had her cats cut out of and stolen from her Acura in the parking lot in SoCal where she worked. I'm not saying cats can't or won't go ever go bad, but isn't that the last thing you'd replace, after all the relevant sensors?

 

If DTC P0430 and or P0420 are present and the MIL is on, replacing the catalyst on the corresponding side is how it can be cleared permanently.

Did the engine have constant misfire events that caused the MIL to flash?

 

Negative. No misfires. In fact, I had never seen that P0430 code myself while I owned the vehicle.

Only codes I saw many weeks prior were P2122 (related to throttle position / pedal, and also what was causing limp mode I believe) and P013E which looks like it was downstream o2?

I'll remind the buyer about the second code. I would think we'd replace that sensor at a minimum and drive a bit before going for the far more expensive cat?

 

It's a 2016, buyer already approached dealer about extended 8 yr / 80k warranty on o2 / smog stuffs, apparently missed it by just 6 months w/ only 28k miles on the vehicle.

 

The "catalyst inefficiency" can be caused by a bad catalytic converter but also by one or more bad O2 sensors. The system compares the sensor output from before the cat with that after, and expects them to be different because the cat is working. If you have a bad sensor or a bad cat you can get that code.

 

The cat went bad on my '14 Range Rover, according to the codes. In an attempt to avoid the expense of a cat, I replaced the O2 sensors, one at a time, but the bad cat code came back each time. I ended up replacing the cat anyway and wasted the cost of the O2 sensors. Just a data point for you.

 

Did it have two cats? Did the other one go bad at some point?

No electronics, no moving parts, just a honey comb that costs 2-3 grand, each. Not the kind of thing you just throw at a problem hoping it works. To your point, O2's aren't a guarantee, but I'd feel really dumb if it were the other way around -- if I replaced the cat and it turned out to be O2's.

 

I'd clear the codes, run one or two bottles of Cataclean as per instructions first to see if the codes return then address any O2 sensor related to the main code/cat. Only then I'd be looking to replace the cat.