Speedometer/Tach zeroes but truck still runs

[dakata24]

My girlfriends' 1999 Mercedes ML430 had her speedometer/tach zero out completely while she was driving on the highway this morning. The truck ran normally even though everything was showing zero.

Now yesterday, one of her front tires blew out on the highway so roadside service came and jacked her truck up to grab the spare and put it on.

Could the service person have done something while jacking up the truck, removing the spare from the wheel well, and replacing the tire mess up the speedometer/tach to zero out or is it just plain coincidence?

I'd appreciate any advice. Thanks

 

[njmodi]

Is the CEL lit?

Sounds like a fault vehicle speed sensor... the only way it's related to the tire-change is if they bumped the wire/connector going to the transmission (for the VSS) while changing out the tire.

 

[Demon-Xanth]

Check to make sure the blowing out tire didn't break the wires to one of the ABS sensors on that wheel. If the speed sensor on that wheel is gone, the computer could just get confused and go for a "safe" reading.

 

[Nyati13]

Originally posted by: Demon-Xanth
Check to make sure the blowing out tire didn't break the wires to one of the ABS sensors on that wheel. If the speed sensor on that wheel is gone, the computer could just get confused and go for a "safe" reading.

Right, it's far more likely that the tire blowing out is what caused whatever damage occured, than the roadside assistance guy changing the tire.

 

[dakata24]

thanks everyone for your comments.

i'll have her take it in to have it checked out.