P0421 "Test Not Complete"

[cham]

P0421 code was triggered today while driving. It corresponds to Warm Up Catalyst Efficiency Below Threshold. Within FORScan, its Status mentions "Test Not Complete". Is there a chance the PCM just needs to run through more tests and it might close out the engine light, or not likely? It's been pretty cold this past week not knowing if this could be a factor. I chose not to reset the DTC for this reason and will drive some more to see if it sorts itself.

There actually is a related TSB (01-016/15) for the P0421 code which requires a control logic update for the PCM but my VIN is technically just outside the specified effected VINs within the TSB.

Curious if anyone has experience with a P0421 code on CX5s and can weigh in on possible reasons. We've got a 2016.5 CX-5 2.5L NA model. Below is a screenshot of code freeze frame data from FORScan. Red arrow shows what I'm talking about.

 

[Rx7bestJDM]

P0421 usually won’t clear on its own once the light is set; cold weather can delay the test but won’t cause the code by itself, so if it returns after the monitor completes, you’re likely looking at a catalyst or PCM logic issue, and a scanner like the YOUCANIC UCAN II C PRO helps confirm this by monitoring readiness and O2 data.

 

[cz5gt]

P0421 code was triggered today while driving. It corresponds to Warm Up Catalyst Efficiency Below Threshold. Within FORScan, its Status mentions "Test Not Complete". Is there a chance the PCM just needs to run through more tests and it might close out the engine light, or not likely? It's been pretty cold this past week not knowing if this could be a factor. I chose not to reset the DTC for this reason and will drive some more to see if it sorts itself.

There actually is a related TSB (01-016/15) for the P0421 code which requires a control logic update for the PCM but my VIN is technically just outside the specified effected VINs within the TSB.

Curious if anyone has experience with a P0421 code on CX5s and can weigh in on possible reasons. We've got a 2016.5 CX-5 2.5L NA model. Below is a screenshot of code freeze frame data from FORScan. Red arrow shows what I'm talking about.



View attachment 379727

how are your spark plugs and what fuel do you put?

btw forscan can show o2 and other params. You can verify the o2 sensor.

 

[cham]

@Rx7bestJDM @cz5gt So the light just cleared on its own this morning funny enough 10 minutes into the drive. I’ll scan with FORScan to see if the code is still stored but that’s at least somewhat encouraging. Is it possible VINs outside the TSB could still be effected?

Spark plugs still have around 20,000 miles left on their interval if you go by the 75,000 mile change interval. We use 87 octane but from top tier gas stations like Shell or Exxon. Possible there may have been more condensation/water in the gas tanks from rapidly changing temps?

I’ll tried to read O2 params but I’ve never been very good at discerning them and knowing when they’re good or not.

Do you guys recommend any injector/fuel system cleaners, I’m little skeptical of some as it sounds like there is risk of damaging the cats.