1996 ford exploror trouble codes

That combination of codes is peculiar. 125 says you are not going into closed loop. Low temperature.

171 and 174 say O2s have detected a lean condition. In open loop the mixture is predetermined.

PO125
Check the connections and wires for the coolant temperature sensor. Check the operation of the sensor itself.

po171 and 174
Possible solutions include:

In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure

A code P0401 most likely means one or more of the following has happened:

The DPF (differential pressure) sensor is faulty and needs to be replaced. [b:b2e41f1fd3]Big problem for Ford.[/b:b2e41f1fd3]
There is a blockage in the EGR (most likely carbon buildup)
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum

Let us know what you find.

try the coolant temperature sensor first