Our fire department has a 2009 Freightliner with a 2008 OM46O (MBE 4000?) Mercedes that has about 7000 miles on it that was bought new. We are a small volunteer department that gets about 25 calls a year. This thing threw a code about a year and a half ago that the egr valve had a mechanical malfunction (146/7). I replaced the valve but couldn't see anything wrong, not excessively dirty or anything like that. Now a year and a half and less than 1000 miles later it is doing the same thing. I have looked through the procedure for trouble shooting this code and it tells me to check the egr temp sensor. I can't find a sensor anywhere on or near the egr system so I doubt that's a problem. The truck is derated when the light is on, just curious if anyone has any ideas. All I have to check codes is a Blue Point code reader, I do have quite a bit of information but what I have doesn't seem to match up with this motor. I hate Freightliners with Mercedes, I like pre 2007 Kenworths with Cats!
There are some electrical checks you can do as outlined in the Detroit Service Information Bulletin 09 03-18. With that said, the EGR valve is probably plugged up or stuck. The truck is hardly used and probably idles a lot. I would remove it and try cleaning it. There is lots of advice in other threads about cleaning them. Or, just replace it. I unfortunately have been babysitting one of these engines in Freightliner M2 with a 5000 gallon tank. It delivers Unleaded to a gas station once a week on a Island. Like a 10 mile round trip going 35 mph. Probably very similar duty cycle as your departments. I have to service the egr valve once a year. I’ll clean them one time and replace them the next time. Most of the time.
Thanks Coaldust, I guess I am kind of glad to hear this one is acting normal even though that is pretty lousy service. I will try to clean it and see how long it lasts.
EGR valve is a common issue with the 4000, coaldust is correct clean once replace the second time. But the 4000 is a critter all to it's self with a bad history.
I am finding that out, the problem is we are probably going to try to keep it around a while. The truck it replaced was a 1965 GMC with a 401 V-6. I miss it more and more. The other truck is a 1986 C series Ford with a 3208, it never misses a beat.
Those were the bees knees. If you need parts just look up and down, lots of FDs are getting rid of them for a few thousand dollars, I personally know of 4 here in the local area just sitting and rotting.