boblydon

Hi Guys,
My 2010 ML350 outside/ambient temp sensor is reading 85 degrees centigrade and is putting the MIL lamp on.
I have replaced the sensor and it made no difference.
Can i check the sensor and wiring??, what ohms/volts should i be looking for?.
I presume the 85degrees is the default setting?
thanks for reading, any advice would be appreciated.
Bob

Plutoe

Could be loads of things--find someone with factory or equal software if you are looking for a quick resolution---else bla bla

boblydon

All ready done that, star shows the code for ambient temp sensor fault, but does not give any further info

ItalianJoe1

Check the wiring to the sensor itself. odds are they are shorted somewhere. I would have to look up the design on that particular one but usually if it's open (sensor disconnected or wire broken) the temp will be max negative value (-40f or so normally), but if the wires are touching it will go max high (85c sound about right). Trace the harness back up to where it meets the front SAM and check for any damage to the harness. I've seen rodents chew through ABS sensor wires up by the battery and cause all sorts of strange codes.

boblydon

Thanks for the reply, will check the wiring back this weekend,which sam does it go to?
Bob

ItalianJoe1

Should be the front SAM, the one under the hood. I'd have to confirm on the diagram but usually the engine bay stuff goes to that one. Although hood switches go to the rear SAM on some cars for whatever reason.

boblydon

Hi Guys,
Thanks for taking the time to answer, just an update to the repair.
After loads of looking and testing resistance,voltage and continuity i traced the fault to the multi plug that connects the wiring harness from the loom to the bumper, the orange wire pin was not making contact.
All working and sorted.
Bob

ItalianJoe1

Glad you found it, always nice when it's something simple to fix that you can actually find.