2001 Dodge Ram 1500 will not go pass 40mph

Is the check engine light on?

Yes, it stays on. The sensor is broke

You are stuck in the limp mode, bring the car to Auto Zone or Advance Auto Parts and they will read the codes for free..

Not in Calif Auto-Zone will not. O'Reilly's will

Ok thank you. I will take it.

Will they be able to tell me why its not going faster than 40

No. They- if they do an OBDII scan- will give you a fault code... and maybe try to sell you something but not give you a reliable diagnosis of why it's in limp mode. Write down the P-code and come back here and myself or one of us will give you advice. But what sensor do you mean is broke?