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Stan
Stan, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3526
Experience:  Technical support engineer
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Have an Atego 1823 year 2001. Keeps going into limp mode, but

Resolved Question:

Have an Atego 1823 year 2001. Keeps going into limp mode, but can turn on next day and truck runs well and normally, then 20 minutes later can go back to limp mode. Have had ECU repaired and told its fine. Any ideas would be much appreciated as I am at a loss and it seems too good to scrap the truck
Submitted: 2 years ago.
Category: Mercedes
Expert:  Shantal-Mod replied 2 years ago.
Hello,
I'm Shantal and I'm a moderator for this topic.
I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.
I was checking to see if you had already found your answer or if you still need assistance from one of the Professionals.
Please let me know if you wish to continue waiting or if you would like for us to close your question?
Thank you,
Shantal
Customer: replied 2 years ago.
Yes please could you still try to find someone to look at our question as still needing assistance. Awaiting a reply
Thank you
Expert:  Stan replied 2 years ago.
Hello,It would really help to know the fault codes stored in the engine control unit and the VIN of your Atego.Best Regards,Stan
Customer: replied 2 years ago.
Stan just getting information for you wanted will be in touch this evening
Customer: replied 2 years ago.
Hi Stan,
VIN WDB9525032K736713 035B114T Engine Type OM906LA111/2. When trucks running correctly the computer shows no faults to be found, when it is in limp modeit it is not communicating to the computer. Occasionally on the truck screen when it is running in limp mode MR appears
Expert:  Stan replied 2 years ago.
Hello,

I would reccomend to check the fault codes with Star Diagnosis computer. Some independent MB workshops have this tool besides the dealers. This computer has the possiblity to access the engine control unit (MR) directly
MR is the engine control unit. It is important to know what does the FR tell when the problem is present.FR sends the engine torque request to the MR so it must have some clues to what is happening with MR.
If MR is confirmed to run well on the other lorry, engine wiring harness must be load-tested . Some of the wires might give poor contact, or the ignition voltage supply from base module could be interrupted, which can lead to lost communication.

Click here for MR wiring diagram

Best regards,
Stan
Customer: replied 2 years ago.
Hi Stan,
Have given the information to my Dad that you have sent, could you please tell me what the initials FR stand for as he doesn't know what it means
Many thanks
Kate
Expert:  Stan replied 2 years ago.
Hello Kate,
FR is German for Fahr Regelung, or drive control unit. FR is it's designation in diagnostic programs and wiring diagrams FR communicates with engine control unit.

regards,
Stan
Customer: replied 2 years ago.
Hi Stan
Thank you very much for your advice and help, still trying to sort out the truck but my dad is very appreciative of your input. Just one last question and I will rate you as unfair to keep coming back.
Yesterday when my dad was driving the truck, for the first time it went on its own back from limp mode that it started out in from turning on ignition to running normally for quite a while, then as usual back into limp mode.
Any ideas would be appreciated.
Many thanks
Kate
Expert:  Stan replied 2 years ago.
Hello Kate,

This can happen if there is an intermittent poor contact in the wiring of engine control unit.
So i must recommend the same steps as in my initial responce ( diagnostic test of all electronic control units with Star Diagnosis computer and load test of the wiring harness).
You can always get back to me, even after rating the answer. Will do my best to support you whenever it is most convenient for you.

Best Regards,
Stan
Stan, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3526
Experience: Technical support engineer
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