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Hi MBWorld. I am a newly registered "member", with a problem that I was hoping some longtime w203 Mercedes owners could provide some insight on.
I have a 2005 C230 Kompressor Sport that has 139,6xx miles, and it threw a CEL with the code P0420. I took it to a mechanic and he was telling me that there are two catalytic converters (that are in line), and the upper one can be replaced no problem, but that the lower may be obsolete, otherwise rendering my car irreparable if that was the problem. I live in California and most of the aftermarket cats are illegal due to non-CARB compliance. One of the things I am having trouble with is, I can't find the lower catalytic converter or any information on it anywhere online. Does my car really have two catalytic converters or does it maybe only have one because its an inline 4? I am not very smart when it comes to Mercedes, this is my first Benz.
Also, what should I do if my car does have two, and it ends up being the lower catalytic converter? It's illegal to buy a used one in California, and if new ones are obsolete and impossible to get, am I basically screwed? My car will not pass smog until this is fixed (if it can be fixed). I also read that gas mileage would drop when the cat goes bad. Just today I drove approx. 50 miles and my car said i got 25 MPG. Any help is appreciated.
Last edited by realw203trent; Feb 4, 2019 at 09:50 PM.
So, as it turns out, my upstream catalytic converter integrated with the manifold, and my mechanic wants $1,234 for one. I found a "genuine" one from www.genuinemercedesparts.com for $909 (minus shipping cost if any), as another member on the forums suggested this website for genuine mercedes parts. Would this fit on my 2005 C230 Kompressor? And if so, what oxygen sensors should I choose to go with it, since he also said my O2 sensors are bad (not sure why, but he said it took them both out). I found this downstream one because on my paperwork it says "DENSO - Oxygen Sensor - Downstream", so i looked for downstream denso o2 sensors and this is the only one that came up for my car. I also found a bosch upstream o2 sensor, but it doesn't say that it's heated. Do both O2 sensors have to be heated sensors or what's the significance in these? I don't know what my car came with from factory.
Sorry to be repetitive, it's probably fine, but the O2 sensors don't have to be heated do they? The mechanic listed a regular upstream sensor but a denso downstream, and when I searched denso downstream sensors, the only one I found was a heated downstream O2 sensor. I'm only asking to completely clarify, because while I want to get this fixed, this is the most money I've ever spent on something online, and would hate to make a mistake.
Last edited by realw203trent; Feb 10, 2019 at 03:28 PM.
That will show you the correct part numbers for your car.
As far as I know, the W203 C230's did not have a special version for Calf. But, I may be wrong.
When I put my VIN into the MB EPC parts number software (I access), I get the same part numbers.
Hey, thanks for the reply. I put in my VIN and the same manifold/cat came up, so I guess that's the right one. But multiple oxygen sensors come up, so would the ones that you showed me from pelican parts work on my car? I'm still confused on the heated/not heated thing. If it doesn't matter, I'll just get an upstream and downstream Bosch sensors from pelican parts.
Hey, thanks for the reply. I put in my VIN and the same manifold/cat came up, so I guess that's the right one. But multiple oxygen sensors come up, so would the ones that you showed me from pelican parts work on my car? I'm still confused on the heated/not heated thing. If it doesn't matter, I'll just get an upstream and downstream Bosch sensors from pelican parts.
But, are all of the part numbers the same for the primary and secondary sensors?
Take a screen shot and post to the forum. Or, post your VIN.
I took a screenshot of all the options on geniunembparts and then i took a screenshot of the ones on pelican parts, and put a red box around the ones i chose.
If you notice, there are only two parts numbers listed:
002-540-06-17 - Always the rear sensor - downstream - secondary.
003-542-73-18 - Always the front sensor - upstream - primary.
So, you selected the correct sensors.
Yea, having multiple descriptions for the same part can get confusing. Unfortunately, it's common. Good Luck!
Btw, your engine is a ticking time bomb.
It has a cheap timing chain. If it breaks, the engine is trash.
Also, often before it breaks, it will become so loose that it will strip the $$$$ cams/gear.
*I* suggest replacing the timing chain every 70K miles.
Fwiw, with the proper preventive maintenance, the car and engine can last a very long time.
Without it, you now understand one of the reasons why used W203s are often very cheap.
Many independents can replace the timing chain on an M271 "cheaply" (iirc, well under $1,000). It's not a hard nor very long job - as long as the existing timing chain hasn't become too loose, and then f*****ed up the gears and cams.
Thanks for the information. I'm just under 140k, assuming it's never been done, I guess i should have been on my second chain right about now, but I definitely am keeping that in my upcoming maintenance because I love this car and would hate to render it useless. Is there a chain that was made to prevent damage, or do i just have to get it replaced with the same bad one every 70k?
I apologize for the necrobump, but I came back here because I seek advice for a new problem I have recently acquired, not posting it on this thread. But I wanted to just close this up and post a nice ending, I won't disclose how I obtained it, but I got an exhaust manifold and had it installed, code gone and car smogged, *WAS* driving it very happily!
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