I was driving at a normal highway speed (75 +/-) and happened to look at my speedometer and saw that it said that I was going 100mph. This freaked me out because it didn't feel like 100. I toggled to the digital reading and it read 75. It remained 25 mph high at other speeds too. Any idea why this would happen? It is a 2012 E350 bluetec. Sorry that photo is a little blurry.

 

looks like its reading kph in the pix, but i dont see how that could happen. so whats it read at a stop, or 25mph etc

 

It returned, slowly, to zero after I shut the engine off. I restarted the engine and the needle remained at zero. I haven't driven it since.

BTW, at 25 it read 50

 

Do you have an MB-specific scanner? If possible please scan the vehicle to see if there is any CAN communication error code recently reported. Copy/Photo them, and clear all the codes, drive it for a few minutes, and re-scan again.

 

I took it out for a spin today and the speedo seems to be working okay, if it does it again I'll put the scanner on it. But I'd still like to know why it went crazy.

 

You can still scan it to see if there is a stored code, not current.

 

speedo displays erroneous data

Your pick :

• scan for all modules current/stored faults
• clean driver side footwell GND screws
• Xentry the details out of IC module
• Reboot car

Was the vehicle subject to rain intrusion? Any signs of wetness?

 

No evidence of rain intrusion, garage kept and it hasn't rained here since spring. The grounds look good. It seems to be working okay now. It must have been a weird day for my speedo.

 

1-- Related GND reported okay.

2-- Speedo works normally after restart... could be a CAN disruption​​​​​ - Deep SCAN the vehicle! What is the Bosch ESP up to?

3-- I am guessing something is preventing IC from collecting data but ....
> Actually IC shows correct digital data, clock dial itself maybe jamming.
Take a look at IC Module.