My engine check light came on tonight, I went a parts store and they did a code check. The code was "P1507"( I'm not sure about the letter but the numbers are correct). They said it was something to do with the speed sensor. Is this something I could replace to avoid the cost of dealers? I did complete a spark plug and wires replacement with the help of people from this fourm a while back. The engine is the 24 valve Duratec engine.

The P code is probably accurate. The "P" stands for Powertrain. However, the P1507 is not for the vehicle speed sensor, but rather the Idle Air Control which controls engine idle speed. The precise code is "Idle Air Control (IAC) Underspeed Error." Per the factory service manual, "This DTC is set when the PCM detects engine idle speed that is less than the desired rpm."

Possible causes are:

IAC circuit open
IAC circuit short to PWR
VPWR to IAC solenoid open
Air inlet is plugged
Damaged IAC solenoid
Damaged PCM A couple of diagnostic tips are:

The IAC solenoid resistance is from 6 to 13 ohms
Disconnect IAC valve and look for no change in engine rpm as an indication of a stuck or damaged valve If you'd like a copy of the factory service manual section that describes how to troubleshoot this code, send me a private message with your request and an e-mail address for you that can accept PDF attachments.

-Rod