2003 Aerio "Service Engine Soon" light

[Ken M]

Hello everyone. I just purchased a 2003 Aerio AWD to get me through an exceptionally snowy winter. If you like skiing, this is the place to be (Southern Interior BC....Harper Mountain; Sun Peaks on Todd Mountain)
I have just under 200 km's on the car since buying it last Thursday. I bought it from Zimmerautosport in Kamloops, BC, who used to be the franchised dealer. The car was serviced before I took delivery (oil & filters).
The engine check light came on yesterday. I have an OBD check tool. Can you tell me where to find the diagnostic port, please? It is -10C today, so I want to spend a minimul amount of time searching for it.
Also, the car did not come with the normal handbook. Is it possible to buy one?
Thank you, Ken.

[Ken M]

Zimmer Auto Sport very kindly showed me where the diagnostic port is located and, also, read the code which was P0420, meaning "Catalytic converter performing below spec". I had the same code on my Miata. It finally boiled down to cleaning the throttle body and the intake manifold. Any ideas what might be causing the problem with this car?
The light came back on when I drove home (about 35km's up the mountain).
When I connected my universal OBD reader, it showed "Error" several times. I tested it in my Miata right away where it worked normally. Any ideas?
Please!? Happy New Year, everyone. Ken.

[Ken M]

So far, I'm talking to myself but hope springs eternal in the hearts of believers. I managed to borrow a scanner so that I can conyinue to delete the P0420 code. I'm leaning toward something other than a catalytic converte problem. I do have a very slight exhaust manifold gasket leak. I suspect, however, that the problem is related to dirty throttle body and inlet manifold. I thought about using the cleaning sprays available at the local auto factors but I'm concerned that it may damage one or other of the sensors. Any opinions?
I have added injector cleaner to a tank of gas but to no avail so far. All suggestions gratefully recieved. Cheers, Ken.

[lumpylarry]

In my experience it will most likely need the front cat converter..
You can try to clean or replace the downstream o2 sensor..
But that will usually not help.

The cat is monitored by comparing the signals of the rear o2 sensor to the front 02.
When an oil change is done, often the oil from the filter drips right on that bottom o2 affecting its performance. But that will usually give a code p0137
O2 sensor circuit performance.

But doesn't hurt to try and clean it.

Good luck.

[Ken M]

Thank you. The front one is so blessed expensive. Oh well.

[226k]

I have not been on the site in a while. Did you install a new cat yet? How many kms do you have on your car?

I have had the service engine light off and on for about a year in one of my 04 Aerios with the same P0420 code. It first came on at about 166,000 km soon after I got the car used. It seems that the light frequently comes on during wet weather (of course it takes several trips in the car before it resets itself). During the summer it stayed off for months. It also stayed off during a multi day, few thousand km, road trip in the summer. Late last spring I bought what looks like a very good used cat (from an aerio that got wrecked at only 5000km) but I have not bothered to install it yet. My other, higher mileage, 2004 Aerio that I bought new, and which now has266,000 kms, has never had the light come on yet.

[Ken M]

Hi 226K, thanks for your reply. I bought my Aerio @ 158,004km's. I have done just over one thousand since then. I have been able to borrow a scan tool to read the codes and delete them. The light comes on usually on a cruise type of driving but not at any specific interval. Sometimes, it will come on within a very short distance after I have turned it off. Other times I'm good for over 200 km's. I'm not sure that it is caused by a faulty catalytic converter because it is just a flash reading and not permanent. When I'm able to, I turn it off immediately and it will stay off for at least until the end of that journey.
I had the same problem with my Miata, which turned out to be a dirty inlet manifold and throttle body. Right now, it is way too cold for me to even think about working on it. It is to be a winter car only so I will probably wait until more clement weather to try the same same "cure" on the Aerio.
However, all opinions are gratefully received. Cheers, Ken.

[226k]

Interesting. My lower mileage Aerio with the P0420 code was originally from Ontario and also lived some of it's life in central Alberta. Maybe if both our cars have experienced lots of cold weather it has lead to a premature P0420 code. Or maybe it's somehow due to their slightly lower mileage for the year (more time sitting or more shorter trips). On the other hand my higher mileage aerio has lived it's entire life on the west coast with it's milder climate and it rarely ever sits for long times and rarely does short trips. So I wonder if the longer time sitting or short trips leads to excess moisture in an Aerio cat which maybe in turn leads to deterioration of the catalyst material?

Regarding the idea about the dirty throttle body: My higher mileage aerio started having a noticeable resistance to any initial throttle opening. (The gas pedal was sticky until it opened a bit.) So at 240,000 km I cleaned out a lot of gummy carbon from the opening area of the throttle body and off the throttle plate itself, using a rag and a part can of "Air Intake System Cleaner". Thankfully that fixed the sticky gas pedal problem. But throughout that time of having so much carbon buildup the service engine light had never come on (and that is my Aerio that has never had the light come on) So in my experience a very dirty throttle body did not lead to a P0420 code.

Have you seen the info posted about the P0420 code on the "aeriostyle" site? There is a fair bit of info there and I think someone there mentions removing one of their O2 sensors and cleaning it as helping the issue - similar to what Larry suggests above. I am considering trying that sometime before I actually bother to change the cat.

[Ken M]

Hi 226k, my car spent the majority of it's life in the Victoria area. It was purchased locally by the father of the owner who lived(s) in Victoria. The car was traded back to the original dealer by the father for a new SUV.
I have not seen the aeriostyle site. Is it part of the Suzuki site?

[White Car Black Roof]

I've seen quite a few Aerio's with bad Cat's.
Too bad yours is an /03 cuz they have 8 years factory warranty on them.
Has any one tried any of the after market Cat's out there?
I've seen them on e-bay for 2-300.00 + shipping which isn't cheep either but it might save you some gas money.