I had 6 cel codes. P0300 random misfire, P0243 turbo solenoid/transducer, P0400 egr flow, P380 glow plug heater, P0110 intake temperature sensor ,P0100 mass air flow sensor.
Did some work and was able to get all of the cel codes fixed except for P0100 and P0400. What puzzles me is that I did the mass air flow and egr fixes using resistors and capacitors per the tapatalk instructions. To be honest these were the codes I didn't expect to see again.
I did notice that after I was able to delete the other codes from the system the idle sounded much better. I haven't taken the car out to see if the turbo is functional and if the car runs fine even though there are 2 codes present so that remains to be seen.
Is there something I can do other than disable the fixes I've done to the mass air flow and egr systems?
Final note. I did the cel delete with the engine running. Could clearing the remaining 2 codes be done without the engine running and would that prevent them from coming back on.
Roddy

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OM606 turbo I assume

If you have a bad MAF you will get the P0100 fo MAF failure, and the P0400 for EGR issue (because it uses the air flow value via the MAF to determine if the EGR is working).

I would try replacing the MAF. Note the OE MAF is a couple hundred. But with a little sleuthing you can find the Bosch sensor online for much less. You will need the HF tamper proof bit kit to get it out.

You can try MAF cleaner but in my experience that is a fool’s errand.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

I bought a new maf so I'm pretty sure it's fine. But I did the maf delete and I might've got a bad resistor so I'll be checking that out. I have a tester and I'll check the resistor installed and a fresh one to see if that's the problem. After all you can't take anything for granted. If the resistor checks out then I'll return the maf wiring to stock and see if that remedies the problem.
I read the maf fix would work without the maf being plugged in. And I tried that too. Same results.
Not concerned with the egr until I get the maf fault cleared. I have the egr transducer removed per the egr delete instructions and I'm hoping that won't need to be attended to. BTW I did change the egr transducer with the turbo transducer and that cleared up the turbo transducer cel code.
Another thing I repeatedly pulled a vacuum on the egr valve and released vacuum many times until I could hear the egr valve close. I think that helped the idle.
I drove the car around the neighborhood and the turbo is working. Not near as good as my old 85 300sd but I can finally tell the turbo is doing something. And the idle is much improved so going in the right direction.


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Thanks for posting at least basic descriptions with the code numbers. Too many people post numbers along with " Tell me what part to change because I don't want to make an effort " .

Be aware that a detailed code description is critical to efficient diagnosis. For example, the extended description for " P0100 mass air flow sensor " might include : MAF voltage out of range low / MAF voltage out of range high / MAF voltage erratic / MAF voltage implausible. This info would be found in a service manual / better scan tools. Low end scan tools tend to give the short generic description that leads to random parts replacement.

Hang a volt meter on the MAF output and have a look. Don't 100 % rely on scan tool readings, sometimes the ECM will substitute a plausible value during a failure that the scan tool will pickup.

If this is a W210, they have issues with under hood grounds.

Also if W210 , the MAF has a 12 volt source from the cars wiring to power it up the electronics and a 5 volt source from the ECM that is modified for MAF signal out.

I checked the ecm voltage to the maf sensor and got 5.01 volts.
I checked the resistor on the car with my spares and they were spot on.
So I returned the maf wiring to stock.
Ran another scan and the maf (P0100) trouble code is now gone.
But I still have the egr (P0400) trouble code. I know the egr transducer is bad so putting that on won't work. I ordered a replacement but it hasn't arrived yet.
Not sure why the maf and egr fixes didn't work. Was very disappointed to find that out.
I'll update when I get the replacement transducer.
I'll report how the maf affected performance later.
Roddy

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In a nutshell the EGR prove cycle works like this. Doing this from memory so if I have something wrong let me know.

When the engine has achieved operation and stabilized, the EGR prove cycle is started. The EGR valve is opened a defined amount, and the mass air flow is monitored, to make sure the air volume passing the MAF dropped by a predicted amount. This predicted amount is based on how much exhaust gas (coming through the EGR) the computer thinks the engine should be producing for the given operating point.

If your EGR vacuum transducer is not working then the EGR valve cannot open. The computer senses the lack of EGR valve opening and throws a P0400.

The diode/resistor hack works to fool the MAF sensed voltage input to the computer, when the EGR transducer is actuated. The resistor and diode couple some of the voltage used to pull the transducer open into the line for the MAF, thus fooling the computer.

I ended up removing my EGR hack that the prior owner installed on my W210 because it was causing issues with P0400 codes being thrown if the car was started if you forgot to wait the whole glow cycle when it was cold. Which happened every time I let a stranger (repair shop, valet park, my kids until they figured it out) drive the car. So I ended up removing the diode/resistor, and the obstruction in the EGR vacuum hose, and putting the system back to stock.

If changing the EGR vacuum transducer does not fix the problem you will probably need to scan with the HHT emulator found in Xentry. This goes through the 38 pin port in the fuse box under the hood and provides system level access to the computer. The OBDII port was a first gen implementation and it only passes the federally minimum required emission test codes to meet the law as it was in 1996. Of course on modern cars you can get complete access through the OBDII, but that does not work on a W210 from the late 90s. An iCarSoft or other third party OBDII connected high level scanner will not get any more data from a W210 than a generic code reader.

I thought of one other thing. You said that you had to pump the EGR valve numerous times to get it to cycle. I would pull the intake manifold/EGR and give everything a good cleaning and get the EGR valve operating properly.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Took the 1999 e300 for a short drive and it's rather sluggish in first and second. But in 3rd through 5th it has a little turbo action. But I expected more.
I'm hoping a new egr transducer will make the difference.
BTW I didn't notice any performance gain after getting the maf trouble code removed.
I thought the 606 was supposed to run way better than the om617. So far the old om617 is the better performing engine. But I know the om606 gets way better fuel mileage so there's that.
My guess is the ecm is limiting fuel enrichment and turbo boost due to the egr flow issue. That has to be the performance problem at the moment.
Keep in mind I bought the car with the cel on and haven't really experienced a good running 1999 e300 yet. So far not impressed but hoping once the egr issue is resolved the performance will be there.
Miss the old mechanical Mercedes diesel. Was very straight forward and predictable.
Roddy

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Did you measure the 12 V supply and the output of the MAF? Finding the extended description of the P0100 mass air flow sensor code will point you in the correct direction.

You are stuck in limp mode (reduced performance) due to the P0400.

It will take off like a startled cat (well it does take a moment for the boost to build) once you get it sorted.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

I'll update as soon as I get the new egr/turbo transducer installed.
Roddy

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Got the transducer finally. In about 10 minutes I got the cel off.
Keep expecting to see the cel come back on but it hasn't.
Took the car for a brief drive and it's a totally different car.
Remember I bought the car with the cel on so I haven't experienced the actual performance. It runs very clean and runs quite strong.
Roddy

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Update
The car was still very sluggish off idle to around 2000 rpm.
Did some research and was informed to change the fuel filters. I replaced all including the fuel tank screen.
Made a noticeable difference.
Roddy

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