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Hello everyone, I am posting this for posterity as I have just been through a several month long adventure getting my 2006 E320 CDI running right again. I have had full access to WIS, Startek, and PTSS case information through the entire process, all of which were nearly useless in this specific case. Hopefully in the future I can help someone out who gets the same codes and has the same problems, or combination of problems and help them avoid a bunch of confusion.

The Background -

A few months ago I started intermittently getting a CEL and a fault for the o2 sensor value and o2 sensor heater (will edit to add generic and SDS codes) and noticed the car seemed to be smoking more than the occasional puff when accelerating hard. It seemed like it had plenty of power and normal smoke at the top end, but rolled coal under part load. The car has over 300,000 miles and I replaced the turbo last fall when the bearing failed and it dumped a bunch of oil into the exhaust. Naturally, I replaced the o2 sensor with an OEM part, cleared the code and reset all adaptations thinking it was just a routine repair. The smoking did not get any better and generic faults P2071, P2073, and P2076 (SDS faults 2076-002, 2028-004, 2028-006). Specifically confusing until researching in WIS and elsewhere about wideband o2 sensors were the faults 2028-004 "Pump Current G3/2 (O2 sensor upstream of KAT)) oxygen sensor battery severely discharged/ faulty" and 2076-002 "Check component G3/2 (O2 sensor upstream KAT) value below limit". Long story short, ALL THESE CODES MEAN IS THAT THE CAR IS RUNNING RICH!!!! They have nothing to do with the actual O2 sensor being faulty even though the SDS tells you to test the O2 sensor, and it will pass every time. (Also, there is no actual value for the O2 sensor in the SDS so you are better off using an aftermarket scanner to monitor the signal and compare with a car that runs right.) I checked all wiring from the O2 connector to the CDI module and front SAM and found no issues of corrosion or intermittent contact. I swapped out the MAF cartridge since it was $40 no luck. Brake boosted the car and listened for leaks and found nothing. Swapped out the rail pressure sensor and pressure control valve because I had a spare fuel rail available, no help. Then I found the intake port shutoff flap motor linkage broken and the flaps stuck partially closed. I removed the intake manifold and cleaned/deleted the shutoff flaps. (There is no position sensor so no CEL when it breaks like the 642, but you can also delete it and just leave the motor plugged in and no CEL.) This also did nothing to fix the code or smoking. At this point I started wondering if there was something going on with the boost pressure, though the scanner was showing max boost values near 21 PSI I became suspicious. Since a new boost pressure sensor was cheaper than a trustworthy quality gauge I put one on. Shortly thereafter the car started going into limp mode (opens vanes in turbine so it wont make any boost) and got codes for low boost (SDS code 2359-001 "Check charge air system. Too low boost pressure") and because I had removed the air filter box/heat shield and replaced with a cone filter to look at the operation of the vane position actuator on the turbine a code for the MAF (SDS code 2011-001 Check component B2/5 (hot film mass air flow sensor). Sensitivity drift air mass ratio for calculated quantity (top).") At this point I was finally able to drive another car with a 648 that came in to the dealer and compare live data, which was all pretty much the same except that my 02 readings were extremely low and my car would go into limp mode. So I decided to recheck for a boost leak and noticed oil all over the back of the fan control unit. I leak tested the charge pipes again and they had finally cracked enough for the leak to become obvious. I replaced the dry rotted rubber charge pipes, reinstalled the factory air filter box (cone filter directly on the mass airflow sensor will cause code 2011-001), and reset the mean quantity adaptation. The car is back to full power and normal low smoke levels.

Conclusion -

1. If you get codes P2071, P2073, and P2076 (SDS faults 2076-002, 2028-004, 2028-006) they likely mean your car is running rich, not that the 02 sensor is bad.

2. Check the condition of charge hoses, specifically downstream of the intercooler. If it/they is/are hard or look dry rotted just replace it first and go from there.

3. Check the intake shutoff port linkage, if it breaks it will not set a related fault code because there are no position sensors like the 642 and gas motors.

4. Swap out the boost pressure sensor or hook up a mechanical gauge to verify boost reading.

5. If that hasn't fixed it possibly look into the VGT position actuator motor on the turbo intermittently having issues (I'm pretty sure the actuator is the same as the 642 and various other VGT turbodiesels)


Hopefully this saves someone some time and helps with confusion about what these O2 sensor codes mean. At least its out there now for the next dealer tech that resorts to google because WIS/Startek are no help.
 

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Ok you deleted the swirl flap motor but did you secure the flaps in the open position? It takes a lot of WOT spurts to finally clean the pipes. I think it took about three weeks of heavy driving to clean up the exhaust.
 

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Discussion Starter #3
Ok you deleted the swirl flap motor but did you secure the flaps in the open position? It takes a lot of WOT spurts to finally clean the pipes. I think it took about three weeks of heavy driving to clean up the exhaust.
Deleted as in took everything out, tapped the holes in the manifold and plugged with a bolt and seal rings. The motor is just bolted to the manifold with no linkage and plugged in so it doesn't set a code. This was just an issue I found along the way and how I dealt with it so it cant happen again.

The issue was the boost "seep" through the small dry rot cracks in the rubber charge pipes and possibly that coupled with the boost pressure sensor. The pipes leaked enough to make the car run rich at part load but not enough for the car to pick up on a low boost condition. Once I replaced the boost pressure sensor (which I believe was reading high) I think the additional boost finished growing the small cracks to the point where it would leak enough to set the low boost code.
 

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when you were reading all these OBDII codes, did you ever get a chance to scan with DAS? OBDII codes are intentionally generic and vague, you need an OEM scanner to be able to read codes that are more specific. i know for instance, my 07 E320 bluetec had the same issue you're having with your CDI, and it ended up being split open rubber hoses to/from the inter-cooler like you had. the codes however, pointed to low boost pressure yet DIDN'T throw a check engine light or any OBDII codes!
 

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Discussion Starter #5
when you were reading all these OBDII codes, did you ever get a chance to scan with DAS? OBDII codes are intentionally generic and vague, you need an OEM scanner to be able to read codes that are more specific. i know for instance, my 07 E320 bluetec had the same issue you're having with your CDI, and it ended up being split open rubber hoses to/from the inter-cooler like you had. the codes however, pointed to low boost pressure yet DIDN'T throw a check engine light or any OBDII codes!
Yes, I am a dealer technician with access to any information (short of what engineering keeps secret from everyone to make our jobs significantly more difficult). The SDS codes 2028-004 "Pump Current G3/2 (O2 sensor upstream of KAT)) oxygen sensor battery severely discharged/ faulty" and 2076-002 "Check component G3/2 (O2 sensor upstream KAT) value below limit" have no worthwhile information available through Mercedes. Everything available suggests a wiring issue, faulty O2 sensor, or defective CDI control module. I was just sharing so the next time someone working in a shop googles the faults because there is no factory information they would be lead here. In my case it may have been a combination of a few parts, but I believe that the small cracks in the hose were enough to effect the fuel mixture at part load, but not enough to trip a low boost code until the cracks grew over the course of a several months. I'm used to seeing the charge hoses rip/blow out on various diesels and they are usually very easy to find because you can hear them and live data values for boost and MAF are way out of range. In my case the live data values were only slightly different from a normal car to the point of suspecting the 300+k mile sensors may be off because of age. I should mention that most of the live data had to be captured via generic scan tool because it isn't availible with SDS, particularly the O2 sensor voltage on the OM648 cars.
 

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Thanks for sharing your experience and knowledge. I'm a 25+ year enthusiast who was a high-line mechanic years ago, and even with an SDS in my shop there are still things that can't easily be determined...
 
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