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Registered
98 ML320
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10 Posts
Discussion Starter #1
My truck is stuck in low range (low range light is on). It drives like a bus and won't shift. Occasionally, the low range light turns off by itself when cruising for ~3 seconds and it can shift again, only to turn back on right after.

These are my codes:

ETC
041:

"[One or more messages from control unit N78 (Transfer case control module) are intermittently not available on the CAN bus or the transfer case position is position is intermittently implausible.] or [One or more messages from control unit N78(Transfer case control module) are not available on the CAN bus or the transfer case position is implausible.]
DTC Status: Resistance too low"

137:

"One or more messages from control unit N78 (Transfer case control module) are intermittently not available on the CAN bus.
DTC Status: Resistance too high"

AAM
B1040-003:

"CAN BUS: communication control: N78(distributor drive control module)
DTC Status: Stored"

I have tried clearing the codes, but they still remain. "Low Range" Light is on 99% of the time. I read somewhere that I must replace the transfer case motor (as they are prone to fail). Is this correct? If so, is there an updated transfer case motor (where they corrected this flaw and what is the part number)? Should I get a genuine MB part or an aftermarket like Dorman? When installed, do I have to clear the codes again or is there just gonna be no "low range" light?

Thanks in advance.
 

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Registered
2003 ml500, 2004 ml350
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942 Posts
Please add your year and model click up right avatar, account settings scroll down to vehicles.

Because we have no idea what model and year you have.
 

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Registered
98 ML320
Joined
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10 Posts
Discussion Starter #4
You'll probably think I'm lying but was just on by itself. It turns on and off by itself (like mentioned before). It's off for 3 seconds at times (even if I didn't put it in neutral).
 

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Registered
2003 ml500, 2004 ml350
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942 Posts
You'll probably think I'm lying but was just on by itself. It turns on and off by itself (like mentioned before). It's off for 3 seconds at times (even if I didn't put it in neutral).
When you say that do you mean just the light goes off or it physically disengages for 3 seconds?

If it disengages low then your motor is working, and Witek thinking about the module is on track. Have you left the sunroof open during a downpour?
 

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Registered
98 ML320
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10 Posts
Discussion Starter #8
When you say that do you mean just the light goes off or it physically disengages for 3 seconds?

If it disengages low then your motor is working, and Witek thinking about the module is on track. Have you left the sunroof open during a downpour?
I believe it’s both because when the light is off, the truck shifts fine. My sunroof is always closed and I have never spilled my drink on it.
 

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Registered
2003 ml500, 2004 ml350
Joined
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942 Posts
I am on my phone so don’t have access to the wiring diagrams. But if there is a relay involved here I wonder is it sticking shut? If there is try replacing/ swapping see if problem persists. Very inexpensive check.
 

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Registered
Dallas, Texas
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7,154 Posts
No relays involved. Fuse F1f8 battery power, fuse F1f22 ignition on.
 
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