Hi guys,


This is Tommy Woo, I'm new here, I own a 2009 Miata 6AT and I bought an used 2005 RX8 6MT (170KW edition) recently.

This RX8 worked fine when I tested driving it, but, one day, when I connect a OBD cable and read the ECU state, I noticed the error code P0038 in my O2 senser which located in CAT.


I talked with some engineer in Mazda maintenance center, they have no idea on it because Mazda has stopped shipping RX8 to China from 2009. They got a used O2 senser from another broken RX-8 and tested, it also reported the same issue, so they believed just replacing the senser is not enough.


At this scenario, they can't fix it and they thought it's useless to replace the senser with a new one (In China, I need to pay 200$ for that and wait for one month, there's no new one for testing).


The engineer suggested me to continue driving it as "this error won't make any issue, just increase the oil consumption".



I don't care about MPG, as I can still afford it. But I'm curiuos if I keep driving it with the P0038, will there any negative impact for the engine output? I haven't tested driving a new RX-8, so it's very hard for me to verify if mine is working fine. The previous owner replaced the engine with a new one and it has been running for more than 7K mile so far, and I'm satify with the power after 4,000 RPM, but I'm not sure if the engine can perform better after fixing this issue.


Will such P0038 will decrease the horsepower? And is there any other way which I can try to find the very point of this problem?

Thanks.

 

The o2 sensor in the cat isn't a huge deal if it is messed up. If the wideband front o2 sensor gets messed up that would be a serious problem but the rear one wont cause you major issues. Do you have a cat on the car?

 

The CAT should still be there, but I'm not sure if it's still working, because I found exhaust is much more smelly than my Miata. (Even I warm up the engine after 10 minutes driving).

 

If the exhaust has the rotary stink, it's probably failed. If it's melted or plugged, the engine will be damaged, and both power and efficiency will fall.

 

thats a rear o2 sensor code and its mostly a failed sensor(circuit on high usually means there is a short internally)

and yes if the exhaust smells like rotten egg 90% chance the cat has failed.

u in china? im in hong kong now and. can give u some help, pm me

 

Hmm, currently, I feel bad performance under 4000RPM, but it's good after 4000RPM. Can I say the engine might be still good at this moment?


BTW, I can als use OBD cable to read the driving state.

Most under 4000RPM, it's in "Closed Loop - Error" state.
If I keep in high RPM, it goes to "Open Loop - Driving" state.

The closed loop with error is not very good for me.

 

In Shanghai, so it's very far away from your location.

I'm thinking to replace a new rare O2 senser for a try, someone say it's waste of money if CAT has failed. Should I pay some engineer to open my CAT and have a look?

 

Well, I actually will visit Shanghai, i have friend who lives there, i just don't have the time yet.

Anyway, it shouldn't cost too much to have them drop the pipe to look at it.

the rear O2 sensor does not affect performance in ANY WAY. it just there to check CAT efficiency.