My check engine light came on recently and returned codes P0401, P0174 and P0171 with my clone FORD VCM2. I don’t recall the exact descriptions off top but a quick search will return those. Basically P0401 is an EGR-related issue and the other two are lean codes for both banks.
I found a lot of information which lead me to the following course of action. For P0401, remove and clean the EGR valve. For P0171 and P0174, everything pointed to a faulty mass air flow sensor. It was about 50/50 on whether to clean or replace the sensor. I read a lot about cleaning the throttle body in this process to removed the caked up deposits on the backside of the butterfly valve.
I decided to do the following:
1) clean the EGR valve with basic carb/choke cleaner; removing EGR valve requires replacement of the gasket; There is a metal tube that feeds into the air intake from the EGR valve. The tip of this tube had a lot of black, crusty carbon deposits. This must be removed. The tip of this tube can be found on the inside of the air intake behind the throttle body. I just reached in with a finger and Q-tip and was able to remove it all.
2) clean the mass air flow sensor (requires cleaner specific to this part)
3) clean the throttle body (also used cleaner specific to the part)
I disconnected the negative battery terminal for a half hour or so to reset the computer. Once all the cleaning was finished, I cranked the truck up, no CEL. Looks like this simple cleaning was all that was needed. Additionally, I’m hoping this improves the fuel economy. I have also noticed a little quicker acceleration.
I think I about covered it all. Hope this helps.
This is from obd tool website technical support: 2001 Explorer Sport P0401, P0174, P0171 CEL Problem Solved