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A technical question about sensors for Emissions Test
So I’ve had my RX8 for just over a year now and it used to be in Florida where I didn’t have to worry about emissions testing so I was never to concerned about my CEL coming on for the P0420 code because of the Hi-flow cat that came with it (it was the previous owner’ track vehicle). Anyway I just replaced the battery which reset the sensors and moved to Missouri where I need to have it pass emissions to get registered very soon since the DMVs are reopened. I used my own OBD2 scanner which is informing me the Evap System, Catalyst, O2 Sensor, and Secondary air pump are “not passing” but I still only get a CEL for the P0420 code. Is this caused by the sensors not being able to set as “ready” because of the catalyst being below threshold?
I have scheduled an appointment at the dealership to Have my catalytic converter replaced and I’m hoping that it will allow all of the sensors to be ready once that is cleared up because it is the only CEL I am getting. Has anybody else experienced similar issues when getting their RX8 up to passing a smog check?
I have read over the threads on here about sensor readiness but I can’t think of anywhere that I could safely perform some of the driving modes that are suggested for setting the sensors.
it almost always means a bad catalytic converter. Some people will claim it can be the rear O2 sensor, but the sensor has it’s own trouble codes. Evap System is a test known to take a while. There should be an allowance for either one or two tests to still be open/incomplete and get an OBD2 pass, but it varies by state & specific location.
Is the air pump on the car and functioning? Some of the aftermarket tuning devices can “stealth” some of the codes, but generally the parts like sensors and such have to be in place for it to do that. It could stealth that code, but not a missing air pump as an example.
Thanks for the quick reply. Currently the engine control System is all stock, I removed the piggyback when I bought the car which led to a whole host of other problems that I got sorted out. But for the most part I can hear the whining noise that I would associate with an air pump when the conditions would cause the air pump to run, and I’m not getting any other codes that would suggest a part failure (it’s a 2004 with 42k miles and was maintained meticulously). I’m really hoping the it’s just the catalyst keeping the sensors from setting as ready, but I want to have as much info going into the dealership as possible to try and keep this as cheap as possible since I was unemployed for 10 weeks and was denied all benefits for some reason.
ok, my apology for glancing past your actual question; I’m not sure if that alone causes them not to set. I never had that problem either with an OEM or aftermarket cat. I can’t recall it ever being discussed or asked before, but will snoop around some and look for an answer.
Thanks for being so helpful with this, but you don’t need to go through all that trouble for me. If you happen to come across somebody who has an answer definitely send them my way. I’m gonna researching this at least an hour a day for the next week myself lol. My only other car before this was a 1973 240Z so sensors and emissions are totally new me and it sounds like the sensors on an RX8 are a real PITA to get ready.
Thanks for the quick reply. Currently the engine control System is all stock, I removed the piggyback when I bought the car which led to a whole host of other problems that I got sorted out. But for the most part I can hear the whining noise that I would associate with an air pump when the conditions would cause the air pump to run, and I’m not getting any other codes that would suggest a part failure (it’s a 2004 with 42k miles and was maintained meticulously). I’m really hoping the it’s just the catalyst keeping the sensors from setting as ready, but I want to have as much info going into the dealership as possible to try and keep this as cheap as possible since I was unemployed for 10 weeks and was denied all benefits for some reason.
The air pump only turns on when you start the car cold for about 20 seconds then shuts off. If you are getting a code it’s worth investigating. This is of course if your cat is still healthy. If you end up having to go catless (like many of us), you can just remove the air pump and block it off. Did you check to see if it’s turning on during a cold start?
If it ends up being a damaged cat, you can buy a cheap aftermarket cat and a midpipe and just swap the cheap cat in for emissions but actually drive the car with the midpipe.
Last edited by CaymanRotary; 06-10-2020 at 12:28 AM.
the only code is P0420, it’s the initialization tests that aren’t setting and he’s asking if the bad cat is influencing those.
stick to just the info near the beginning of this thread, some foolishness in the middle, with an extra dose of snarky at the end for dessert. I miss 9k
And after you swap the battery and have a known good catalytic convertor in.. will take a bout 3-5 days of cold starts and driving to clear up all of the codes. I tried doing it all in a day and it was a waste of time. It’s cold starts plus duration of cold starts plus I'm sure many other tests during that test phase.
like how many in a row are successful etc..
Like team said there are tolerances allowed during the smog testing process.. rule of thumb for myself is 2 weeks prior to wanting to pass the test I put the cat on. drive it to and from work for a week, then get it checked. If you swapped the battery give yourself 2 weeks if it’s not a daily driver. Just be patient. Now if you have issues after that... then start chasing codes.
Quick update, ran the emissions test on my OBD2 scan tool when I got to work this morning and monitored it a bit while driving. The Secondary Air system now reads as “passed” and i heard it operate with the cold start this morning so that may have just been a error with my tool yesterday. Now only my evap system, 02 sensor and catalyst are not passing/not ready. Interestingly my scan tool is telling me that my car is passing the heated catalyst system test.
Quick update, ran the emissions test on my OBD2 scan tool when I got to work this morning and monitored it a bit while driving. The Secondary Air system now reads as “passed” and i heard it operate with the cold start this morning so that may have just been a error with my tool yesterday. Now only my evap system, 02 sensor and catalyst are not passing/not ready. Interestingly my scan tool is telling me that my car is passing the heated catalyst system test.
Catalyst should be taken down and inspected. These are commonly toast on RX-8's due to the amount of oil that runs through the engine (and unburnt fuel due to the car running rich). This is why a midpipe is preferable as it will never cause you issues other than the P0420 code.
Last edited by CaymanRotary; 06-10-2020 at 12:44 PM.
So I got my car back yesterday with a new catalyst and passenger motor mount. Set me back a pretty penny $1600 for the catalyst and $400 for the motor mount, but they showed me my old one and that mount was shot to hell (I’ve got no shaking anymore though which is nice). All of my sensor set except for my EVAP system still, but I can pass a state emissions with one incomplete monitor. My buddy did however accidentally clear my DTC codes after Setting the sensors so I gotta drive it again to get the catalyst to set lol. I should pass emissions now but I’m bummed by how expensive the cat is but hopefully I can get another 40k miles out of this one.
However after getting my car back I’ve now got some universal codes pending on my car U1900 and U0073. Which say that the “data bus is OFF” which seems weird because everything is running and functioning just fine. The emissions test they ran after the cat install shows that U0121, U0155, U0167 were present during the test but those have not resurfaced on my scan tool since my friend accidentally wiped the DTC codes when we were testing if the monitors were ready. Like I said everything seems to operate fine like it did before the new cat so does anybody know if these are just erroneous errors being reported due maybe as a result of the dealership unplugging and plugging things back in during the install?
06-09-2020, 07:01 PM
