I had the codes pulled due to a "check engine light" on my 99 Mountaineer, they were P0401 (EGR Flow Insufficient) and P100 (OBD Systems Readiness Test Not Complete). Can anyone tell me what they really mean and what is likely cause? What should I replace? Thanks!

 

SEARCH this forum for "P0401" threads. Most likely problems will be caused by faulty DPFE sensor or clogged EGR inlet path. Also possible - the EVR solenoid or the EGR vlave, or other vacuum or electrical lines in the EGR system.

The P1000 (not 100) code indicates that the computer has recently been reset and has not had the chance to sucessfully run all its self tests. This code can be ignored unless you are attempting to get the vehicle ready for OBD-II emissions testing, in which case the systems must be in operating order (your's isn't) and all self tests must have been run sucessfully. This normall takes several error-free drive cycles.

Steve