On my 2009 Lancer ES, the service light came on. A friend of mine who is a mechanic checked the code and came up as P500.. The mechanic said it's for a speed sensor. When I went to price the speed sensor at my local auto supply, I found out there's 2 separate sensors. An Input and Output Sensor. Has anyone else had this code before? If, yes, what did you replace?

 

I had this issue with my input speed sensor, car would not accelerate properly. I decided to replace both the input and output speed sensor.
The output sensor seemed ok, but I had the budget to replace it also, since it would probably fail also sooner or later.

 

I was leaning towards replacing both as well .