SL/R231: OBD codes - PO442 and 456
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Joined: Feb 2023
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2015 SL400
OBD codes - PO442 and 456
Fellow MBers,
My latest adventure with my 2015 SL400 is a check engine light with no other symptoms. My generic ODBII reader finds PO442 and PO456, which both have the same description: "Small EVAP system leak". I've checked the gas cap and it seems fine.
Before I haul this to my favorite garage, I'm looking for any advice you might have.
But please note, below, the problem I reported 18 months ago - a strong in cabin odor that I've never been able to solve...if anything, it's getting stronger. Luckily, I really enjoy top down driving.
Friends;
For the last month, I've experienced a strange smell in the cabin that seems to come from the AC vents, whether the AC is running or not. My indy repair shop confirmed it is not R134. They also said no leaks or anything unusual could be found. No codes present, either. I replaced the cabin filter, but it didn't help. Can't detect the odor under the hood, only in the cabin.
I would describe it as a "chemical" smell, or maybe like a high end glue. Yes, it gives me another reason to drive with the top down, but I think something is wrong.
Since I don't really want to sniff glue whenever I'm driving, I'm wondering if any of you have any experience with this kind of thing?
Dave in Fort Myers, FL
My latest adventure with my 2015 SL400 is a check engine light with no other symptoms. My generic ODBII reader finds PO442 and PO456, which both have the same description: "Small EVAP system leak". I've checked the gas cap and it seems fine.
Before I haul this to my favorite garage, I'm looking for any advice you might have.
But please note, below, the problem I reported 18 months ago - a strong in cabin odor that I've never been able to solve...if anything, it's getting stronger. Luckily, I really enjoy top down driving.
Friends;
For the last month, I've experienced a strange smell in the cabin that seems to come from the AC vents, whether the AC is running or not. My indy repair shop confirmed it is not R134. They also said no leaks or anything unusual could be found. No codes present, either. I replaced the cabin filter, but it didn't help. Can't detect the odor under the hood, only in the cabin.
I would describe it as a "chemical" smell, or maybe like a high end glue. Yes, it gives me another reason to drive with the top down, but I think something is wrong.
Since I don't really want to sniff glue whenever I'm driving, I'm wondering if any of you have any experience with this kind of thing?
Dave in Fort Myers, FL
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Joined: Feb 2021
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From: Nor-Cal
2020 GLC300 -2014 Sl550 - 1997 SL600
I haven’t heard of such problems with the R231 but know some mb’s did suffer from fuel tank cover plate leaks. If everything else checks out it may be worth a look.
I think that if you got the car scanned with XENTRY, You would probably get more insight as to the particular codes being triggered. The codes you list are generic OBD codes.
The smell may be a non related issue. AC related (or other) vs fuel evap).
Does the AC work normally?
Does the car show any interior work? Does it have the optional leather dash? Maybe someone tried to glue down the dash cover as those have a tendency to lift/bubble in the Florida heat & humidity. See if you can get the VMI (Vehicle Master Inquiry) from your local dealer.
It’s a fairly common issue for cars with a leather dash. It seems to happen a lot in Florida for some reason….
Good Luck
I think that if you got the car scanned with XENTRY, You would probably get more insight as to the particular codes being triggered. The codes you list are generic OBD codes.
The smell may be a non related issue. AC related (or other) vs fuel evap).
Does the AC work normally?
It’s a fairly common issue for cars with a leather dash. It seems to happen a lot in Florida for some reason….
Good Luck
Last edited by crconsulting; Aug 1, 2025 at 10:13 AM.
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Joined: Aug 2021
Posts: 109
Likes: 13
2015 SL63 AMG (R231)
Hi
R123a is nearly odourless its not OTT unpleasant but is a slight chemical odour and you more likely to smell the oil that goes within the R123a
Getting the gas pressures checked is often cheap takes minutes or even free in UK just pay if it needs topping up
All AC loses gas from the compressor shalt seals over years so low gas does not mean in must be in the cabin
If its like bad socks etc its likely as CR said to be mould/microbial growth in the drain pan from a blocked drain line or elsewhere in the ducts under the dash in the system
AC expert will have spray to get ride of it
Batteries if the small 8mm?gas line not connected can also smell and old ones even if it is connected
R123a is nearly odourless its not OTT unpleasant but is a slight chemical odour and you more likely to smell the oil that goes within the R123a
Getting the gas pressures checked is often cheap takes minutes or even free in UK just pay if it needs topping up
All AC loses gas from the compressor shalt seals over years so low gas does not mean in must be in the cabin
If its like bad socks etc its likely as CR said to be mould/microbial growth in the drain pan from a blocked drain line or elsewhere in the ducts under the dash in the system
AC expert will have spray to get ride of it
Batteries if the small 8mm?gas line not connected can also smell and old ones even if it is connected
