The 2007-2010 Silverado, Sierra; 2001-2007 Silverado Classic, Sierra Classic; and 2003-2010 Kodiak and Topkick equipped with the Allison LCT1000 transmission (RPO M74, MW7) may have a delayed engagement or no engagement into Drive, a delayed engagement or no engagement into Reverse, or a range inhibit with several possible DTCs.
TIP: These conditions may be more pronounced in cold climates during a cold start.
When DTC P0701, P0751, P0756, P0761, P0843, P0848, P0873, P0877 or P0894 set, it could indicate no or excessively low pump pressure as a result of a no prime or loss of prime condition within the transmission pump. Follow the diagnostic steps outlined in the Service Information.
All of these DTCs, excluding P0894 could be set due to a fluid service/filter change, transmission service involving removing the pan, low fluid level caused by a leak, or long periods of storage.
Also check the transmission fluid level using the Hot Check Procedure. Low fluid level may cause any of the listed DTCs to set, particularly during a cold ambient and cold vehicle start. In cold climates, ensure the fluid level is at the top of the HOT band.
After checking the fluid level using the Hot Check Procedure, if any of the DTCs reset during a cold start, inspect the internal suction filter for possible cracks.
TIP: Replacing the TCM will not likely correct any of the listed DTCs or low main line pressure.
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