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P1621 Diagnostic Trouble Code Discussion for March 2009

Control Module Long Term Memory Performance

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Trouble Ticket Help Requests for DTC P1621
Help Request Posted
2004 GMC Sierra 3500 SLE 6.6L Hesitation, Surge VIN: 1GTJK33254
P1621: Control Module Long Term Memory Performance. This truck came in and it bucked on accel. After sitting all night it ran fine.I believe it is a fuel issue and at one moment I thought I saw fuel pressure drop off on the modis. Any help on this would be helpful as I am not a diesel tech. I changed fuel filt...
March 03, 2009