2010 XC60 T6 - Eternal P0420 Topic is solved

[jhock]

I too would not expect a code to pop up for the thermostat. My 2010 T6 was not warming up sufficiently in the winter (air in the cabin would never quite get warm) so I got an OBDII reader and sure enough the temp never got over 80C even in stop and go downtown traffic for 45 minutes. Changed my thermostat and saw exactly what pgill posted, failed in exactly the same way. But it had been that way for at least weeks, maybe longer because I might not have noticed during the warmer weather. Strange to me as heavily as the car monitors itself that it never warned me about the broken thermostat.

I also have the P0420 code pop up about twice a year (usually in the shoulder months and almost always in the Fall), but it always clears itself in about a month or so. When I look at the readings in the test, it is only barely outside the maximum parameters to set the warning. Eventually it takes care of itself, but I am not sure how or why.

[pgill]

J Hock,

That is excellent information.

Thanks for confirming that the Thermostat had failed and that no check engine light was set.

Now if you can please let the MVS collective know if P0420 returns this winter or if the Thermostat made the difference.

I do have the following observation to share with the group

To evaluate the Catalytic converter the ECU at idle will temporarily create a lean mixture and then switch to a rich mixture and it monitors how long before the change is detected by the Oxygen sensor after the Cat.

According to Denso "Lower Cylinder pressures and leaner mixtures require longer ignition time to combust"

Also according to Denso a cold engine needs a richer mixture.

These two factors combined can lead to quenching and the Iridium TT's are advertised as resistant to quenching.

This is the reason why I am switching to the Iridium TT's in my 3.2.

In this context Quenching can be thought of as partial burning. If the air fuel mixture extinguishes when the ECU is trying to check the catalytic converter efficiency then the measurement isn't going to be meaningful and I suspect that is why you get a P0420. As I stated above I fixed my neighbors P0420 (Toyota not Volvo) and the only change was the Iridium TT Sparkplugs.


One last thought the 3.0T is lower compression than the 3.2 which should make it more susceptible to Quenching due to lower cylinder pressure.

Just my $.02


Thanks

Paul

[XC60Newb]

I added the spacer, ran some Techron (two tanks @ recommended Oz/G) and replaced the PCV box because.. well why not at this point. Once I reset the code and the ECU, I went over 1,500 miles without the MIL. I have yet to go more than two tanks without the MIL in literally 4 years. However, after about 1,500 miles (was on a road trip), it came back on. To my surprise, it was NOT the P0420.. it was a P2096 (Post Catalyst Mixture Too Lean). I have now gone almost 3,000 miles without a P0420, so that seems fixed.. but at the expense of another, similar code. My hunch is that this is the same Oxygen sensor, now being far-enough removed from the pipe to read 'too much air'. There are no symptoms.

The vehicle has been and still does runs great. No hard starts, stumbling, misfire, loss of power, etc. It is smooth. Still, I will check all of the vacuum lines, and MAF, and exhaust.. again.. to see if I can get this code to go away. At this point, I honestly don't think there is anything to fix it besides replacing the entire intake, fuel and exhaust system piece by piece, and I will not do that. Every dealer and private Volvo technician that I have been to (2 of each) is stumped. They all say just deal with it, it's just new sensitive sensors and cats and not worth the $$.

I kinda feel like selling it now. Volvo wont stand behind this vehicle or issue any longer, so makes me not want to own another one. The last thing I will say, and which I have told Volvo, these cars are way too smart and the codes are way to common to lack this much specificity. They need to separate the fuel, ignition and exhaust codes out into the various sections of the system, more specificity to identify these codes.

[XC60Newb]

FIXED !! (let's hope I didn't jynx it...) Ok, here's the deal. It's been over 5k miles since I installed the spacer and replaced the PCV Trap. (See my last post) I did both of these things together even though neither were "needed" as the last attempt to fix this problem, hoping (and not caring which one) one of the two would work, permanently. If you read/remember, the PCV trap was checked multiple times by technicians, and had "no issues". It had great vaccuum.. turns out.. actually more than it should have had, which can ALSO cause the p0420 code, whereas most technicians will tell you that unless there is negative vacuum (pressure) then the trap is not bad. The trap may not be bad, but that doesn't mean that the computer isn't sensing something wrong. If the code is unwavering to fixes, and the trap seems fine, you should still try replacing it regardless.

Regardless of whether it was the trap or the O2 spacer, there is one very key piece of the puzzle that was missing, which no technician, dealer, etc. ever mentioned in the 5 years and tons of $$ that I've spent dealing with this issue. You MUST have a technician reset the data "Adaptions" in the computer after replacing any key parts on the catalyst system in order to see if it works (It's cheap/free). The reason why, is because once the computer throws the code, it resets the faulted readings as baseline data points, and uses that new baseline to adapt/adjust internal settings (oxygen, fuel, PCV allowances, spark, catalytic and O2 measurements, etc.). Here is where the problem lays.. if you change or add an important part it may fix the actual problem theoretically, but the computer MAY still use the recently set data baseline to measure against, and when the fix puts the data back into a normal spot, the data shift from the recent (faulty) baseline may still trigger the system to recognize a major change (error), which of course throws the code, even if the new readings are correct. You should "Reset the Adaptions" back to stock/standard values after each solution to be safe.

I need to clarify that this is not always the case, and most times the simple solves or replacements will be corrected through the data properly, and/or the technician will reset the Adaptions properly. However, if you are experiencing an Eternal p0420 code, no matter what you try... this is likely the issue. I have been dealing with this for 5 years and replaced literally everything I could on the catalyst system. My recommendations are // replace the PCV no matter what the assessment comes is (especially before anything expensive), and, have a technician "Reset the Adaptions" after part replacements.

Holler if you have any questions.

[Dzikiewicz]

Sooo hold up they will re baseline the ecu/ECM based off not stock but the condition of our now 10 year old cars? This is logical. But did you have the dealer do this with the O2 sensor spacer? What O2 sensor spacer did you buy ? And how was this service free? Nothing from Volvo is free.

Bit of history ive changed the following parts
-O2 sensor (post cat)
-thermostat
- overpriced PVC valve Volvo calls something else

Cheers

[XC60Newb]

Apparently, the adaptations don't reset just because a new part was installed, and the swings/corrections it reads after the part is installed (if it fixes something) simply tells the computer that another major shift occurred (because it had re-adapted to the new mixture needs) and trigger the CEL again. It's doesn't necessarily happen all the time but it does happen ESPECIALLY after a new PCV is installed - in which case I was told they say you must reset the adaptations (by computer).

I put the 02 sensor and PCV box in myself. The spacer came from IPD, it's about an inch and a half, and the PCV box was a genuine part I bought from a Volvo site for $140-ish. I cleaned the engine steel and ports under the box really good as it was caked with hardened oil deposits. Quick-reset the system with battery disconnect/terminal fusion, and the CEL kept coming back, until I took it in and had the Adaptations reset, fixed instantly. It was not a dealer, but a local Volvo Specialist, which had been doing my diagnosis and other various needs, so he didn't charge anything to hook it up and reset after my install.

I've never touched the thermostat and from what I've read, as well as discussed with technicians, it would never throw a catalyst code alone in this vehicle, especially a p0420. Then again, if it's cheap and easy why not try it I guess.