PIP4379K

File in Section:
Service Bulletin
Bulletin No.:
Date:
PIP4379K
October, 2013
PRELIMINARY INFORMATION
Subject:
Delayed Or No Drive And Or Delayed Or No Reverse With DTCs, Range Inhibit
Models:
2007-2014 Chevrolet Silverado
2003-2010 Chevrolet Kodiak
2001-2007 Chevrolet Silverado Classic
2007-2014 GMC Sierra
2003-2010 GMC Topkick
2001-2007 GMC Sierra Classic
Equipped with The Allison LCT1000 Transmission RPO M74 or MW7
This PI was superseded to update model years. Please discard PIP4379J.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern
Customer may comment on a delayed or no engagement into drive and or delayed or no engagement into reverse
and or a range inhibit with any one of or a combination of the following DTCs P0701, P0731, P0732, P0733, P0734,
P0736, P0751, P0756, P0761, P0776, P0843, P0848, P0873, P0877, P0894 or P2723. This condition may be more
pronounced in cold climates during a cold start.
Recommendation/Instructions
P0701, P0731, P0732, P0733. P0734. P0736, P0751, P0756, P0761, P0776, P0843, P0848, P0873, P0877, P0894
or P2723 could possibly indicate no or excessively low pump pressure as a result of a no prime or loss of prime
condition within the transmission pump. When any of the above DTCs are accompanied by a P0701 begin
troubleshooting with the SI for P0701 first. Be sure to follow all diagnostic steps. With any of the above listed DTCs
follow the SI fluid checking procedure to PROPERLY check the transmission fluid level using the Hot Check
Procedure. Low fluid level may cause one of or a combination of the listed DTCs to set, particularly during a cold
ambient and cold vehicle start.
Note: Ensure the fluid level is at the top of the HOT band when the transmission fluid temperature is 175°F. Refer to
SI document 2408059 for the proper fluid level checking procedure.
DTC P0701, P0731, P0732, P0733, P0734, P0736, P0751, P0756, P0761, P0776, P0843, P0848, P0873, P0877,
P0894 or P2723 can set by the following: fluid service/filter change, transmission service involving removing the pan,
low fluid level caused by leaks, or after long periods of storage.
Note: If the fluid level has been properly checked using the HOT check procedure listed in SI document 2408059
and any of the DTCs reset during a cold start inspect the internal suction filter for possible cracks.
Note: If no other concerns are found inspect for a stuck lube regulator valve (item 13 in document 2384492) in the
pump cover due to debris.
DTC P0894 diagnostics will run during NLT (neutral lock turbine). During NLT the transmission applies 3, 5 and
Reverse clutch and 2, 6 clutch, in conjunction with Low & Reverse clutch already applied to lock turbine shaft. This
feature is only active in combination when engine elevated idle is active to shorten engine and cab warm up time.
This feature is initiated if transmission sump temperature is greater than -25°C (-13°F) and the engine coolant
temperature (ECT) is greater than -40°C (-40°F). If the transmission sump temperature is greater than 60°C (140°F)
or the engine coolant temperature is greater than 60°C (140°F), the NLT feature will terminate.
Important: Replacement of the TCM will not likely correct any of the above DTCs or low main line pressure.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is
resolved without completing every step, the remaining steps do not need to be performed.