2012 XC90 3.2l - P0420 and P0430 Catalyst Below Threshold - VIDA Graphs/Pics

[ChicotheCat]

Hey All!

Long time lurker for my 2007 s40, first time poster with the (new to me) 2012 XC90 3.2l.

Just purchased, vehicle has 160k miles on it and prior maintenance history is unknown. Vehicle appears to run fine, doesn't misfire, etc. but has the dreaded p0420 and p0430 CEL for cats being below threshold - purchased under the impression that the cats would need replaced. There were no other stored codes other than the ignition key light ring.

Dove into it today with VIDA to look into the issue to see if that's what it really was, and I am starting to second guess if it really is the cats.

To my understanding, the downstream (rear) o2 sensors should be pretty much constant, however mine are fluctuating like crazy between .0v volts (downhill, no throttle) and all the way up to ~1v when wide open throttle. The interesting thing is my upstream (manifold) o2 sensors BARELY move off of 1v, to my understanding these are the ones that are supposed to be bouncing between .1v and 9.v. As you can see in the VIDA graphs below (unless I am mistaken?).

This got me thinking that the rear o2 sensors (and cats) are possibly functioning ok, and there is something going on with the front/upstream o2 sensors, causing the vehicle to run super rich, thus flooding the cat with way more than it can handle/supposed to handle, thus triggering the 0420 and 0430 codes.

Haven't dove into much else, pulled the plug out of cylinder 1 (new plugs on order), they appear to be original, stamped Volvo and model FK20HQR10. Didn't seem overly bad, carboned up, etc. Gap seemed a little large. Visual inspection under hood doesn't appear to be any vacuum leaks or anything out of the ordinary.

Does my thought process seem correct? Anything really to be looking for? Any starting points? Any other recommended parameters to look at with VIDA to possibly see what's going on?

VIDA graph of both front o2 sensors - VIDA indicated bank 1 threw the code about 9 months ago, and the bank 2 code appeared about 3 months ago, if the timeline stamps are to be trusted. The middle graph line is 1v and the scale was 1 minute graphing and 4 minute graphing. These were graphed while driving on normal city roads.

[pgill]

2012 XC90,

I don't have VIDA/DICE but I do own two 3.2s. And I helped my Neighbor with his Toyota get rid of P0420.

Here is what I would do if I were you

1. Replace those ancient Plugs with DENSO IRIDIUM TT plugs (if you want them to come in a Volvo box then get 31286359) or if you want the equivalent plug without a Volvo logo then get Denso 4704 IKH20TT

Inspect the coil packs to see if they have any cracking or if they smell burnt. Replace the coil packs if they are suspicious.

This is what I did for my Neighbors Toyota and the P0420 disappeared over a year ago.

Note: the Sparkplugs that you have now are single Iridium, the Twin Tip Iridium are advertised to reduce quenching (or misfire if you prefer). I think this is why Volvo switched to the TT Plugs. For reference I have never had a P0420 or P0430 on either of my 3.2s but I do change the sparkplugs every 50,000 miles. (this is the harsh service low quality fuel interval) and I recommend that you do the same.

After you replace the sparkplugs there are other things to look into: PCV, Thermostat, Intake Manifold Gaskets, etc.

Take a look at my S80 3.2 Thread it shows everything that I've done to my 2010 S80 since I purchased it in 2018.

viewtopic.php?f=31&t=87687

Good luck

Paul

PS I recently bought a diagnostic tool that can check MisFire counts and I do get misfires on both of my 3.2s. Typically 1 misfire per cylinder every other time I start it. The Misfire rate is about 0.01% (one per 10,000 roughly). Extremely low yes, but not zero.

2010 S80 3.2

Cylinder..........EWMA (counts)..........Last (counts)..........

Cylinder #1..............1.........................0..........
Cylinder #2..............0.........................0..........
Cylinder #3..............1.........................0.........
Cylinder #4..............0.........................0..........
Cylinder #5..............0.........................1..........
Cylinder #6..............1.........................1.........

If you have Mode $06 data like this it would be helpful

[abscate]

Welcome!


Have a look at fuel trims to see where your fuel mix is. Thst will help track down intake and vacuum leaks.

First posting with VIDA data….you will do well here….

[ChicotheCat]

Thanks for the replies! Got to tear into it a little bit yesterday and swapped out my spark plugs with the recommended ones above (non volvo branded..) and visually looked/listened for any types of vacuum leaks, etc. with none found.

Below are the pictures of my plugs - VIDA does log misfires and zero were detected across a 30 minute drive, including both highway and city driving.

I also did a drive with VIDA graphing the rear o2 sensors (all over the place!) and with fuel trim/RPM. I believe my front o2 sensors are fine as they are sitting around 1, I previously thought this was voltage and should be spiking between .1 and .9, however upon further research, determined that the "1", since it isn't voltage, represents lamda 1, unless I am mistaken?

Not sure what I am looking at with the fuel trim, any analysis and input would be much appreciated.

Plugs:





Fuel w/ Throttle:


Rear o2:


Thanks again.

[pgill]

You are on you way to getting to Stage 0.

Looking at your sparkplugs I would replace the PCV valve.

Here is the reasoning.

The Channel for the Gases that get past the PCV diaphragm connects to all 6 intake ports.

Starting with #6 (the cylinder closest to the battery)

6 - 5 - 4 - 3 - 2 - 1

So if oil gets past the valve it is most likely to go into cylinder #6 and least likely to go into cylinder #5. Edit: #1 is least likely to get oil

Because the sparkplugs are very old I wouldn't blame you if you checked the function of the PCV by removing the oil fill cap with the engine at idle (The Vacuum at the fill cap will be very slight if the PCV is working, if it is broken then the engine will likely surge because you just introduced a vacuum leak)

Here is a write up on how to replace the PCV (you can use the Land Rover part if it is cheaper than the Volvo part but I don't recommend aftermarket get an original part)

https://www.freel2.com/forum/topic32107.html

If you want a laugh then watch the HONK video in this link

https://www.freel2.com/forum/topic37372.html

Thanks

Paul

PS the code that you are fighting is set by the ECU when it evaluates the efficiency of the CAT. I will look for a PDF that explains what happens but basically it is something like this. 1. Run the Bank slightly lean for a few seconds 2. run the bank rich and repeat as needed the go to the next step 3. measure how many milliseconds delay between front O2 and rear O2. The whole test only takes a few seconds and it is only run when the ECU decided the conditions are right. It is unlikely your data actually has the switching inside it.

[pgill]

MY07B6324S-S80XC90AWD (1).pdf

(464.87 KiB) Downloaded 300 times

Here is a PDF from Volvo that explains how things work for the 3.2 with respect to emissions

The document is for a 2007 but I think the emission system is similar if not identical for your 2012



Looking at the document you will find that the upstream sensor is Binary and the Downstream sensor is linear

HEGO = Universal Heated Exhaust Gas Oxygen Sensor = ”Binary sensor”
UHEGO = Universal Heated Exhaust Gas Oxygen Sensor = ”Linear sensor”



Good luck

Paul

[pgill]

There is a good discussion about the 3.2 on the other Volvo board


A link was posted that indicates an exhaust leak in the flex pipe could be the root cause of the code

https://www.swedespeed.com/threads/anot ... st-7881666

Good luck

Paul

[chitownV]

Here is the same topic in the other Volvo board. Working through the codes and graphs.

https://www.swedespeed.com/threads/2012 ... st-7902424