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I've used the STAR system I recently purchased with Jake to address my long-standing Front SAM issue and complete my TPMS retrofit. Now I'm turning my attention to my P0410 and P0420 codes. I have a lot to learn about they system and I hope that someone on the board will point me to resources that will improve my proficiency.
During the time I was working on my SAM issue, I started to get an occasional check engine light. When I first read the codes, my iCarsoft scanner showed P2035-000 and P201d-000 which are not defined in any resource I could locate. I cleared the codes and the check engine light would stay off for about a month or two before coming back. Eventually I was able to read a P0420 (catalytic converter) code with my iCarsoft scanner. When I hooked up the STAR system and used DAS, I could also read a P0410 code. Here's the screen shot:
Fault Codes
Apparently, the P0420 code is the one that illuminates the check engine light. I've reset the CEL several times after each incident, but I now seem to have to reset the light more frequently. I estimate I have to reset it after driving about 160 miles. Before I consider replacing the catalytic converter, I want to rule out all of the possible causes for the P0420 fault. I'm seen some suggestions that the problem with the secondary air injection system (reflected by the P0410 code) or possibly a defective oxygen sensor could cause the problem.
Here's a video I took while using DAS to diagnose the secondary air injection system. It appears to be showing that the reading from the oxygen sensor is below the required value. Is it possible that this is because the oxygen sensor needs to be replace, or is a more complex issue the culprit?
It's one, or some/all of the following:
1) The electric air pump that is used only with a cold engine.
2) The O2 sensor is old, and slow.
3) The cat.
Imho, I suggest you replace them in the above order also. The air pump, and o2 sensors both go bad with age/usage. Neither is horrible to replace - with the right tools. And, neither is "very expensive".
The error indicates that, during the air pumpOBD-II test, the air pump is not leaning out the A/F mixture to the extent/amount expected.
I am having difficulty determining whether the engine in my car has an electric air pump. Some posts I’ve found indicate that the Kompressor engines use the supercharger as the air source for the secondary air injection system.
I found this video on YouTube which shows the system in a 2002 sport coupe:
The author explains how the supercharger is used as an air source. I understand that is the previous generation of engine and that Mercedes may have made a design change for the motor in my car.
I wholeheartedly agree that the catalytic converter is the last part I will consider for replacement. I am trying to avoid ”throwing parts at the car “ by improving my diagnostic skill.
Based on the video for the previous generation engine and RedGray's suggestion, it appears that the next step in my diagnostic process is to check this part for exhaust particle build up or corrosion:
Secondary Air Injection Check Valve
Please let me know if you think I need to take another path.
I looked at the picture I uploaded in the last post and thought I saw something odd near the end of one of the vacuum hoses.
Small defect/chafe mark near the end of the hose
Small but possibly significant hole
I guess it's possible that this was causing a small vacuum leak. The hose was long enough that I could cut off the damaged part and reattach it. I'll see whether it makes a difference.
I didn't erase the codes after cutting off the end of the vacuum hose. The CEL illuminated about 50 miles after I fixed the hose or about 120 miles after the last reset. I will reset it today, but I am not optimistic that was the solution. My next steps will be:
1. Replace all the vacuum hoses. My rationale is that they are all probably 15-years old and if one was damaged the others may have hidden defects. It also isn't expensive.
2. Remove and clean the air pump check valve with carb cleaner as recommended in the YouTube video I linked in a previous post. If anyone accesses this thread in the future, I have posted a picture of the check valve removed from the car below. This is a picture I found on line. The part number for the check valve is 021406260.
I removed and cleaned the EGR check valve. The valve was relatively clean but the tube that attaches it to the exhaust system was full of soot.
It cleaned up pretty well with carburetor cleaner.
If anyone else needs to do this, you need star sockets. I had to access the fasteners that attach the tube to the exhaust system by feeling using different length extension for the top and bottom bolt. Don't let this picture fool you. I took it by holding the camera under the exhaust manifold. You cannot actually see it.
There is a gasket that fits between the EGR tube and the exhaust. It was a little tricky to install, but patience and a good sense of touch paid off.
Unfortunately, I suffered a minor setback during the process. I dropped my socket wrench and it hit the alternator connection to the battery and grounded to the chassis. (That was obviously some bad luck.) I saw a spark and heard a pop. When I started the car to test it, I had the red warning message for an alternator failure. I am planning to replace the voltage regulator and determine whether that will fix the problem. This video gives me some hope that the replacement may be possible with the alternator on the car:
I estimate that it will be about two weeks before I have the car back on the road and drive it enough to see whether cleaning the EGR valve fixed the P0410 code and P0420 code issue. If it didn't, step two will be to replace the EGR check valve and step three will be replacing the oxygen sensor after the CAT. I don't want to contemplate step four - replacing the CAT.
Again, comments and suggestions are appreciated.
Last edited by KevinH2000; May 25, 2020 at 03:24 PM.
I've attached pics from WIS and from the W203 Service DVD.
Note, the Secondary Air Injection valve is a combination A.I.R and EGR valve.
However, the W203/C230 M271 does not use the EGR function.
As far as I can tell, even the later model M271 engines, with direct injection and Turbo-charging, did not use the EGR function.
I hope that clears up some confusion on the functionality of that valve.
Imho, part of it is because WIS is lousy for information, descriptions, and accurate specific car/model information.
Thanks for the information. I know more than when I started. For example the information you posted seems to indicate that air could be injected for up to 150 seconds if the engine required that amount of time to reach 60 degrees Centigrade. I thought it was a maximum of 30 seconds. The secondary air injection seems to have a bigger impact than I thought which may increase the likelihood that it is causing the codes.
I will need to drive about 120 miles without the CEL illuminating before I will even begin to hope that the work I’ve done solved the problem. There was small vacuum leak and significant carbon build up. I think those were issues, but they didn’t seem like they were THE problem.
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