A couple weeks I came on this board looking for help in diagnosing our ’01 Duramax – the pickup would go into limp mode pulling a trailer up a long grade and record the “P0093A” code in storage.

http://www.thedieselpageforums.com/t...ad.php?t=36637

General consensus among local mechanics (GM and others) was that the pickup probably needed new injectors based on its age, mileage, error code, and the general reputation of the LB7. That didn’t make sense to me, as the pickup exhibited NONE of the performance traits of faulty injectors, so I decided to look for help here before going any further. Among the people replying was John Kennedy. Following a few phone calls and e-mails, I decided to follow John’s advice and swap out the original ECM with one of his “tuned” ECMs, as he had a very logical explanation as to what was happening, why, and how he corrects it with his re-programmed ECMs. We installed one of his ECMs yesterday, and after steep grade test drives w/ and w/o a trailer in tow, I believe my problem is solved. Will continue to test and look for signs of physical fuel system problems over the next couple weeks under varying conditions, but initial indications are great:

1. Operating under load with the scan tool attached, my mechanic could immediately see that “actual” fuel pressure tracked very closely with the “desired” fuel pressure using John’s re-programmed ECM. The difference between those 2 values (and the lag in response) was very notable with the original ECM and seemed to be what was triggering the “limp mode”.
2. All attempts to force the pickup to go into limp mode (by repeatedly re-creating the same conditions that caused it previously) all failed. Prior to swapping ECMs, the pickup would go into limp mode quite readily as long as we had our gooseneck trailer in tow. After swapping ECMs, I ran a 5-mile grade quite aggressively w/ the trailer in tow, and it didn’t miss a beat.

Will update my findings again in a few weeks after I’ve got more miles on this ECM, but I strongly suspect Kennedy Diesel has the ’01 Duramax “phantom limp mode” figured out. To anyone faced with a similar situation, I’d suggest at least a call to John prior to going thru a spendy injector replacement.