Trouble Code - PO431 warm up catalyst efficiency - below threshold

Tas4200coupe

Junior Member
Messages
66
#1
Hi fellas, I’ve been struggling with this one for the last week. I’ve cleared it a couple of times but it keeps coming back, so I guess it’s real. The online research I’ve carried out suggests that one of my “cats” has failed and needs replacing (in which case I’d probably replace both sides and maybe upgrade to either the FD or Fabspeed sports cats)? Is this definitely correct though? Alternatively, maybe it’s just a sensor somewhere needing replacement? Has anyone had experience with this error?

A little advice would be most welcome as always.

Many thanks in advance.

Cheers, Kim.

Ps. Loving the new look btw Matt!
 

Tas4200coupe

Junior Member
Messages
66
#3
Thanks Catman but you’ve got me guessing? Sorry to sound completely clueless but where’s the secondary air pump in the exhaust system and which solenoid valves? (I don’t have active exhaust valves btw)

Many thanks again,

Kim.
 

Conaero

Forum Owner
Messages
26,621
#4
Kim, check the metal pipe that runs round the front of the engine. They rot through and cause cat preheat error. The secondary air system blows air into the cats. If it’s not working or the air is leaking out then no cat cooling is in place.
 

GeoffCapes

Centenary Club
Messages
7,394
#5
That was the same message I got on my 4200. The cats failed.
Do you have a white residue on your exhaust tips?

If they have failed, get a good exhaust fabricator to make you some new ones. They will be a lot cheaper than OEM or Larini.

Where are you based?
 
Messages
25,647
#7
Thanks Catman but you’ve got me guessing? Sorry to sound completely clueless but where’s the secondary air pump in the exhaust system and which solenoid valves? (I don’t have active exhaust valves btw)

Many thanks again,

Kim.
Matt's pretty much described it. When your car starts and it sounds like a hairdryer under the bonnet: That's the secondary airpump doing its thing :)
C
 

Tas4200coupe

Junior Member
Messages
66
#9
Ok, thanks for your thoughts everyone. I’ll try to have a poke around over the weekend and report back. I know the jet engine sound (had wondered what it was!) and Matt, I’ll check If I can see what you mean although it is sounding as if this one might be a little beyond my pay grade.

Geoff C, I’m in Tasmania and have no white residue. Was the white residue indicative of cat failure only btw?

Jemgee, do tell!
 

GeoffCapes

Centenary Club
Messages
7,394
#11
Ok, thanks for your thoughts everyone. I’ll try to have a poke around over the weekend and report back. I know the jet engine sound (had wondered what it was!) and Matt, I’ll check If I can see what you mean although it is sounding as if this one might be a little beyond my pay grade.

Geoff C, I’m in Tasmania and have no white residue. Was the white residue indicative of cat failure only btw?

Jemgee, do tell!
The white residue was basically bits of the ceramic stuff in the cats. That's good news if you have no residue, you should be able to discount cat failure then.
 
Messages
66
#12
It’s fixed itself??? One morning last week the light simply wasn’t there? I’ve put the obd reader back on and it is showing no error codes so I’m hoping for the best but I can’t help being a bit unconvinced. It’s due to go in for a service shortly so I’ll have Nino check it out. It does have me scratching my head somewhat ...

Thanks again for all your help and I’ll keep you posted if things change.

Cheers
 
Messages
66
#14
Yep, I can definitely hear the air pump running.

Funny thing though, I was just speaking with my friend Nino (I've mentioned him before on here - probably the best equipped and most knowledgeable Italian car guy in Hobart) and he asked me about the fuel I had been using? I normally us 95 octane fuel and in his view, our 95 is more like your 91. He advised me to only use 98. When I told him that a few weeks ago I had driven to the north of the state and had to refuel at a country filling station that only had 91 he exploded and said that that was my problem right there? I only put half a tank in and promptly topped it up with 95 when I got home. Nevertheless, he was positive that thismay have caused the issue.

Any other opinions on this?

Cheers to all.