Oil temp reading "---" or 0 and oil cooling fan on
 

Anyone experience this issue? My oil temp sensor read 0 today and oil cooling fan ran for about 2 minutes after parking. Oil in engine not an issue. Can we confirm the fan was on because of a fail safe and not anything else other than a failed sensor. Its been a real weird sensor....oil temp readings were all over the place and never seemed to get to operating temp. Ive read through forums and the story never completes so not sure what the final fix was for other folks. Hoping just the sensor and fan was a failsafe measure. Thanks for any input.

Try cleaning the temp sensor connector. The fan on is normal when it doesn't know the temp reading.

https://mbworld.org/forums/c63-amg-w...ing-crazy.html

I had a similar issue in my 07 E63, the oil temp sensors temperature was fluctuating over the place, so I ordered a new one. Once it arrived, I took my car into to Benz elite Automotive in Fairfax, VA to have them diagnose via Star Diagnostics. They ended up changing out the oil temp sensor which isn't easy to get at on a M156 engine, as it resides behind the AC compressor. The sensor was replaced, and they took the car for a test drive, when they returned the primary oil cooler fan was on, and the oil temp showed 215 degrees, which we know wasn't right. So we again replaced that sensor we a new one, then had the sensor reset via Star.
Now my oil temperature ran at about 81 degrees Celsius before the swap, now it run about 87 degrees Celsius which equates to 187 degrees Fahrenheit. And I haven't had any further issues.
So my suggestion, would be to have someone diagnose it with Star Diagnostics. And replace the oil temp sensor, which isn't easy to access or cheap to repair, as it's the labor that gets you.

Ok thanks

Ok got it....yes working on that today...I was more concerned that the fan stayed on....sensor has been ordered.

The fan isn't the issue, its the sensor sending back mis-information to the ECU which is telling the fan that your oil is too dam hot, so turn on the fan to cool it down. :y

Update 2: Been a month since the oil temp sensor replacement....it ran fine for 2 weeks then I started seeing the same fluctuating oil temp...low to hot back to cold......for the last week it has been 145-152 F and blinking no matter how long I drive. Basically saying temp is cold...stumped as to why a new sensor would fail again....does anyone know if there are 2 sensors? Think I read somewhere there were 2? one in block (behind AC) and second at oil cooler? True?

Could be an electrical issue? Loose wires in the connector, pinched wire somewhere etc. They might have knocked it back into place when they replaced it and now it's worked loose again.

Understood...he mentioned that the wiring leading into the old sensor before had oil all over it. He cleaned everything and replaced the new sensor. It’s possible. I’ll have to wait until I bring it in. The oil has been weird for years on my car...constantly fluctuating from hot to cold until it completely died a month ago. Wondering if issues is more than just the sensor now. Thanks will review.

As far as I know there is only one oil temp sensor on the M156. My tech is a certified MB tech, so he would know this stuff. My temp no longer fluctuates, but does read higher than before.

Possibly...he did mention that there was oil in the harness and plug leading to the sensor. Wasnt sure if it was residual from an old spill or new....could not locate leaks.....cleaned best he could and plugged it all back together. Need to check but possibly oil getting into it again.

Performed injector replacement and now everything is normal. Weird but glad it helped. Oil temps warms like normal and is stable.