e320
 

I have a 2000 e320 sedan that is stuck in limp home mode. I replaced the maf sensor because I was told that that could be the problrm, well 400 dollars later and its not working. Does the computer needs to be reset after replacing this part or what do you suggest? Any help will be gladly appreciated.

Hmmmm......limp mode? What's the car actually doing? :confused:

Its obivously something else than the maf. I can look for you if you want just send me your vin.

What caused you to change the MAF? Was the CEL on? Did you read the OBD-II codes? Generally, when the MAF is failing a pair of specific codes are generated. If other codes are present they may indicate other problems such as the CAT's and the O2 sensors. OBD-II codes generally relate to cars emission control systems.

Limp home mode is a feature to protect your car from further damage. You are limited to 2nd gear/reverse and I believe about 2500rpm. So you are not stranded and you can go to the dealer and have the MB codes read with the STAR diagnostics which may indicate a problem with the engine or transmission not covered by the OBD-II codes mentioned above. Good luck.

I was asking him that next.

BTW, qran1, the normal codes for a malfunctional MAF are P0171 and P017x where x is 2 thru 5. P0171 is the actual MAF and the others are fuel trim problems which occur because the MAF is failing.

You can get an inexpensive OBD-II reader (scanner) for about $40 from Harbor Freight. The part no. is 94169. It's normally $59 at the store but often on sale online for $39. Most stores will match the online price if you bring in a copy of the online ad. The connector is under the dash just to the right of the hood release lever. There is a plastic dust cap you must flip open before connecting the scanner. Easy to use. Besides reading any pending codes you can erase them and see if they come back. Sometimes a transient problem throws a code but the problem corrects itself. One example is over filling your gas tank. Unless of course you KEEP over filling your gas tank.:D

This is partially true, if the transmission is in "limp" mode. The throttle is affected when the engine, or traction system goes into "limp". This is why I asked what exactly the car is doing. The term "limp mode" is often used to describe conditions other than actual "limp" mode.

If quan1 will give us a better description of the actual symptoms it'll be easier for us to help.

The OP said "Limp Home Mode" which is a specific MB name for the condition indicating they understand what's happening.

Actually in a CAN based car like the E320 it's the ECU which sets the parameters for 'restricted operation'. It's never the engine or transmission. They just do what they're told:D.

After reading the OP’s original post, it was clear to me that he was using the “limp home mode” term generically. As far as his understanding what’s happening with his car, the fact that he spent $400 bucks to replace the MAF sensor because someone said “that could be the problem”, tells me that he doesn’t know what’s happening. That’s why he’s asking for help, which is what we’re trying to do.



It’s never the engine or transmission??? I’m not sure I understand this.

Which ECU are you referring to that “sets the parameters” for restricted operation? Threads like this prove my point that most people simply don’t understand what “limp mode” really means.

Let me explain. The transmission ECU looks at the internal speed sensors, and gearshift recognition, etc., to determine when to intervene via “limp mode”. As you posted previously, this is to prevent unnecessary damage. When the transmission goes into “limp mode”, you’ll have a very harsh engagement when shifting into R or D, and, as you correctly stated, the transmission will be stuck in 2nd gear. The Check Engine light will come on as well. The reason for the Check Engine light is because there isn’t any “Check Transmission” warning light! If the car were scanned for fault codes in this condition, the engine ECU would simply say to check for fault codes in the transmission ECU.

The engine ECU, (in this case either ME-SFI 2.0 or 2.8), or the traction system ECU determines when throttle control intervention is necessary, via “limp mode”, and again results in the Check Engine light or the ESP warning light being illuminated. This variant of “limp mode” is far less common on MB vehicles.

Now, back to quan1’s problem. What’s your car doing?

I had the exact problem that ILUVMILS just described. The code I was getting from the OBDII scanner was P0715 which points to the speed senson built into the valve body electical plate. This is a dealer item. You have to open the trans fluid pan to get to it. The valve body has to come out before you can replace the electrical plate. Once mine was removes, I could notice some cracks on the speed sensors. I have since replaced mine, but I broke a yellow looking plastic...right by the shift adjuster (not if right name). I actually reassmebled the whole thing before I notice that the car would not move. So I took it apart again, and that was when I noticed that this yellow plastic controlls the pressure within the valve body. I am now looking for that yellow part, so I will not have to purchase the whole valve body....that will suck. I will keep you posted on my results.

Check out this link:

http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=210265&M=112%2E941&GA=722%2E607&CT=GA&cat=23V&SID=27&SGR=100&SGN=10