I have a 2004 expedition flashing code 42. found out code means driverside crash sensor mounting fault. Where is this sensor?

 

You should find it down behind the front bumper, driver's side. This code usually means that ground has been lost at the sensor. Perhaps the bracket has rust and just needs a bit of cleaning.

 

Thank you i will look at that.

 

If that doesn't fix your problem, you may want to look into an ALLDATAdiy.com subscription. There is a ton of info on the Code 42 for your Ford. There are 54 test steps to go through to help isolate the problem within the entire circuit. I attached an image directly from ALLDATAdiy.com showing you where the sensor is.