Trouble codes 171, 174, 137 & 401 came on after engine replacemen

Normally a shop would use a scanner to watch the operation of the EGR valve and sensor.
Code 401 means the sensor is telling the computer the flow is not enough. So the problem could be the sensor rather than the EGR valve. And yes one of the ports could be blocked too.

Go to You Tube Video & watch a video of the entire
EGR System, assuming you have no reference material,
factory manuals & such

Also Google the codes & study

You replaced a part that fails a lot on a ford, but now need
to find out what other item in that system,brought the light on

Need lots more research using the internet, before you start
installing parts

You have to learn how ALL Parts work & how to TEST them

code po412 refers to secondary air injection(AIR) solenoid circuit malfunction Cause may include Wiring---AIR solenoid and ECM I would replace the AIR solenoid or check for power to it first.

PLEASE RATE THIS REPLY FOR ACCURACY

trouble code 340 is for the camshaft sensor , needs replaced

DTC's (trouble codes) are 4 digits long. I am taking it that you mean P0401.Here is a link to a page that explains the code and the possible fixes:

http://www.obd-codes.com/p0401

PO 401 --- EGR Gas Insufficient Flow

There could be more than one reason for that

Have to know the system & diagnose it

Trouble codes are normaly 4 digits with a "P" or "B" before it. I am gonna assume that you meant P0138 and P0401:
P0138 is Oxygen Sensor Circuit High Voltage (Bank 1, Sensor 2)
P0401 is Exhaust Gas Recirculation Flow Insufficient Detected

A code P0138 may mean that one or more of the following has happened:

• Faulty O2 sensor
• Short to battery voltage in O2 sensor signal circuit
• High fuel pressure (not as likely)

Possible Solutions Here are some potential solutions:

• Replace O2 sensor
• Repair short to battery voltage in o2 sensor signal circuit

for info on the P0401:
http://www.obd-codes.com/p0401

Yes you did

PO 401 -- is an egr valve, you could have
bought when you got home, at the local auto
parts store for $90.00 & installed yourself

You never clear any codes or dash check lights
They are used to look up codes & diagnose
OBD2 System issues.

NOTHING goes away.

Those dash lights have been on all
vehicle for 30 years & indicate you have
a sytem malfunction somewhere.

egr position sensor. check items before you replace them, it gets expensive just guessing.

Hi, since the check engine light (CEL) is on you need to get the trouble codes read. Most auto parts stores will do this for free. If there isn't one nearby, any shop should be able to read it (for a charge) or you could buy your own code reader.

The code(s) you'll get will be in the format PXXXX like P0171 or similar. Once you have the codes you can look them up here to get a description - http://www.obd-codes.com/trouble_codes/

Or post the codes back here and we'll help you out. The next step is to get those codes though so you know exactly which areas of the engine to concentrate your diagnosis efforts on. Good luck!