Ok guys... Sunday morning I decided to take my 2003 CLK55 with 143k miles out for a drive... When I did, I found the Check Engine light is ON... my ***** dropped... I drove her the previous night with no lights at all after parking... Not sure what happened overnight...

I took it to Autozone that day and the guy said there was a bunch of O2 sensor and evap codes... So I thought OK this should be fairly easy, emissions is not that hard to work on.. Stupid me, I didn't get a print out of their scan.. So I finally got to borrow a scanner today... CENTECH # 60693..

I pulled these codes.. Note: I got the descriptions and details from http://www.obd-codes.com

STORED: (8 TOTAL)
P0410 - Secondary Air Injection System Malfunction
P0412 - Secondary Air Injection System Switching Valve A Circuit Malfunction
P0444 - Evap. Purge Control Valve Circuit Open
P0403 - Exhaust Gas Recirculation Circuit Malfunction
P0135 - Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
P0155 - 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P0141 - O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
P0161 - Oxygen O2 Sensor Circuit Low Voltage (Bank 2, Sensor 2)

ACTIVE: (1 ONLY)
P0118 - Engine Coolant Temperature Circuit High

I cleared all these codes just to eliminate what was actually stored and active. All codes in stored immediately came back but acted STORED right away... And the 1 ACTIVE code came back as well... Then check engine light came on after a few seconds running..

Everything with the car feels like how it used to be. I cannot feel or see anything different from the drivers cockpit.. I did a quick underhood visual inspection and did not see anything unusual either...

Since most of the codes are related to one another I have a feeling there might be a circuit rub through somewhere on the main harness or the worst thing that could happen...... a bad PCM....

Are there any suggestions from experts out there where I could start? Am I thinking too hard to the point that I am overlooking something simple?

I work in the auto engineering industry and have access to multiple types of diagnostic tools. So all suggestions and advice are welcome.

EDIT: Vehicle is virgin. No mods at all. W209 with m113 non-kompressor. I'm about to take her in for "Service B" but would like to get this out of the way first.

Thanks in advance,
Pat

 

Maybe someone with more experience with the m113 can chime in, but have you checked the basics? Loose gas cap and low battery can cause a plethora of related codes

 

If you have original equipment oxygen sensors, you might want to start by changing them. At this stage, those normal wear parts are past archaic.

 

Yes prznskillz, first thing I checked was the gas cap. I did not check the battery voltage though.

I agree with replacing the sensors but then I just don't like throwing parts at it blindly.

I did a more thorough look around underhood yesterday afternoon. I even removed the airbox and some cowlings inspect further. I did not find anything out of the ordinary. I did see a wire which runs in front of the engine (solid pink and solid blue) and its plastic convolute had deteriorated due to wear and tear. These wires were exposed and sitting on the engine(not good). I inspected the whole wire and did not find any rub through. As I inspected and moved the wire, more of the convolute broke off like sand.

Further, I took home the CENTECH tool and had it plugged in on all 3 drives I did last night and this morning. I cleared the codes prior to driving. All 3 times the P0118 (ACTIVE) did not ever come back but I did notice that my fan would not go full speed when I had the HVAC on full speed.

The other 8 codes would immediately go pending without setting a check engine light. Once I restarted the vehicle and completed a key cycle these codes would go stored and set the check engine light.

I cleared the codes on all 3 drives and did the cycle with the same exact result.

Another observation.. Fuel economy dropped a lot. Codes are emissions related so its pretty much given for this to happen.....

Just to get my biggest worry out of the way... When a Mercedes ECU fails what hard telltales pop up in the cluster? I would assume most lights would be ON given the situation.

Next steps will be testing the battery and lifting up on a hoist to complete underbody inspection.

 

Have you cleaned the MAF?

 

No I have not. I doubt that's what is causing my issue though.

 

Sounds like you have a bad secondary air pump which is prone to failure around your mileage. Also looks like you may need to clear or replace the EGR valves or some components of the EGR systems. Neither of these issues is expensive.

 

This makes sense. The air pump might start the chain reaction in this case.

What factors should I observe for when a secondary air pump fails? I'm reading on how to test these pumps properly..

 

The air pump isn't a cooling device driven by high temps. It's a pollution control device on startup and runs for a very short time to provide extra air into the exhaust manifolds to heat up the catalytic converters quicker. The EGR valves are probably failing or gummed up. You can tell easily enough if the air pump is working. Have someone start the car and listen to see if it comes on. There is a relay that may need to be repalaced, or you may need to replace both the pump and the relay. Here's a good vid on the subject and repairs:

 

I was only really going with that because I have seen something similar to this issue and it was an seemingly unrelated part that was causing all the codes to come up.

 

Thanks floridawriter. I did see that video. I think I verified that my pump is working. I need to check the suction and blowing in the lines on cold start...

Now that I think about it I think I might have had an electrical event the other night. My right license plate light went out. Not really related but could there had been a surge somewhere causing fuses and relays to crap out?

I'll be inspecting all fuses asap and relays when I get a meter.

 

you can even try the old school unplug the battery for a while...people say not to on a modern benz, but only thing ever happened to me was I had to reset automatic windows and sunroof buttons

 

Quick update.... Engine Electrical 15 amp blue fuse was blown. Forgot location, 53 or 54. Replaced it and cleared codes. Now its OK. I'm waiting for the issue to happen again so I can verify cause.

 

Did that fix your issue? Im having the same situation in my SL. thanks