Here is a tip
Had a 99 Cougar with a 2.5 with P0401, low flow EGR. I first tested the EGR with a hand held vacuum pump during idle. Not only did the DPFE reading on the scanner not move but there was no difference in idle speed or quality. Removed the EGR to check operation, open and closed good. But could not blow air through the passage on the intake manifold. Don't waste your time trying to clean it with a wire or blow gun, just remove the throttle body, it's all plugged up right there. Now test it again. The DPFE was reading.42 volts at idle, not high enough, should be about 1.1 volts, so now replace DPFE. Test again with the vacuum pump at idle, all works good now. If the DPFE has been out of commission for a while the ECM won't bother with any EGR operations, I think this is what gets the passage plugged.
Probably same with your truck
Saturday, March 1st, 2014 AT 6:19 AM