PIP4972C

Bulletin No.: PIP4972C
Date: Mar-2013
Subject:
Allison LCT1000 Range Inhibit Or No Forward Reverse P0877 Or P2723 May Be Set
Models:
2001-2007 Chevrolet Silverado Classic
2007-2010 Chevrolet Silverado
2003-2009 Chevrolet Kodiak
2001-2007 GMC Sierra Classic
2007-2010 GMC Sierra
2003-2009 GMC Topkick
Equipped with the Allison LCT1000 Transmission RPO M74 or MW7
This PI was superseded to update model years and recommendations field. Please discard PIP4972B.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern
Some customers may comment that the vehicle will not move in forward or reverse. Codes P0877 Or P2723 may be set.
This condition may occur after the replacement of the spin-on oil filter.
Recommendation/Instructions
Many aftermarket spin-on filters are shipped with a protective shrink-wrap packaging that may inadvertently be introduced into the transmission during filter
installation; this can contribute to a condition where the valve body separator plate orifices can become plugged. Always closely inspect the separator plate for
this condition anytime the valve body is removed.
There are many possible locations where the plastic may lodge. The following are two locations seen on field returned transmissions:
PCS1 feed hole - An intermittent or no reverse condition can be exhibited when the PCS1 feed is blocked along with P2723 setting.
Reverse pressure orifice - Drive range may be inhibited along with P0877 setting.
The most common areas of blockage are shown in the picture below:
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Call out 1
Most common areas of blockage.
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Example of blockage.
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.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may
occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools,
safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that
your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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