I have recently got my first diesel truck (Finally) being a 98 6.5 Turbo Chevy 2500 4X4. Very pleased with it so far but it has come to dissapoint me as I went to get in and drive it today when it started up and began to have a very irratic idle around 1500 and it would surge and the "calibration" felt off with the vehicle shaking at "idle" and almost undrivable. Plugged in the handy Snap-On OBDII scanner and I got the code P1218 which referenced an Injection pump calibration circuit. What exactly is this? I have been led to believe it is something to do with the electronic mudule on the injection pump. Please let me know the problem part and the solution. New to diesel and I need my truck. Thanks.

I talked to my GM dealer and they were telling me to replace the injection pump? THat does not seemt o be the problem but the calibration or after reading up on the truck, could it just be the Pump mounted driver? I am not ready to tear this motor down and put a pump in it yet.http://www.dieselplace.com/forum/smileys/Confused.gif

There is also an optical sensor in the pump... I used to own a 98 6.5 and remember reading a post about changing the optical sensor with out removing the pump... Not sure this is your problem but something to consider other than the PMD. From what I remember PMD problems are usually associated with stalling and are heat related. Good luck...
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I was told by another GM tech that he is almost 99% sure that it is the PMD so I went ahead and ordered one. He said that the code presented by the Computer would have been a P1216 code if it was an optical sensor. I am doing the wrong thing though be using the "part replacement" technique to solve the problem. No onther choice though, need my truck.