Hey every one- newbie here and found the forum while researching a problem we have in our shop. This truck is driving us crazy and I've hit a wall thinking about it. So here's hoping another master tech out there has run into something similar or can look at a scope pattern and tell me what it is!!
This is a 03 ML350- sets curent code C1130 in the ESP as soon as key is turned on- will not erase!! The code is for RR wheel speed sensor-line monitoring (which seems to mean that it is seeing something in shouldn't in the line to that sensor). Car sitting still, RR is sensing 0.4 mph.
Here is where it gets weird- if you unplug the harness at both ends (so no sensor plugged in and no control unit), the wires from that sensor have a pattern in them- Key off!! Main harness was replaced, as MB thought it was the problem- no luck- same thing. It is obviously an induction of somekind, but we have most of the truck unplugged- still there- we can make it stop with unplugging connector #4 from the AAM- tryed a new AAM, same thing. I think the key to this is in the pattern , but I'm stumped as to what it could be- I tryed attached the patterns below, but there are too big, please let me know if anyone wants to see them- I will email them to you- the slower pattern is when the truck is completely at rest, the one that looks like a parade is when the door is open and the dome lights are on.. Any ideas??

Send me the pattern: steveb@atlantic.net If nothing else I'll resize it and post it.

Are you sure you aren't reading florescent lighting from your shop? What is the frequency?

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Seeing as the other 3 sensors don't show it, and the ESP module reads it as that wheel is moving, I can't see it being from the shop- I sent you the pics, Thanks!!

Steve, if you can post the scope pattern I'd like to take a look too.

Here are the patterns, obviously not florescent lights, especially the one with two spikes.

They are really low voltage though. Have you checked the bias voltage from the controller to see if it exists on the wire with the signal. Those sensors are hall units I think, so I'm not sure what the controller sends out if anything.

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__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

PS: that looks like a MODIS, you should be able to take the patterns from it electronically sort of like the pico grab I post below
.

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__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician