3 people reported this problem
PO171-174 Engine codes on Ford F-150
Check engine light with PO 171-174 codes with the 5.4 motor. PCV elbow is leaking vacuum at the connection at the back of the throttle body by the firewall. The vacuum elbow has to be replaced and is available from Ford either with the entire PCV line or just the elbow. make sure you remove the battery cable for 30 seconds after the repair to clear the adaptive memories.
2002 Ford F-150 142,567 mi, Visitor
Service engine soon