Bulletin No.: PI0310C
Date: Nov-2013

Subject:

Loss of Communication with Allison Transmission Control Module (TCM), Intermittent Transmission
Hesitation, Reduced Torque, Range Inhibit, Clunk, Stuck in Gear or in Neutral, Won't Shift, DTC P0880
and/or U0101 Set (Inspect for Electrostatic Discharge (ESD) from Aftermarket Serpentine Belts and/or
Added Equipment, Install OEM Belt, Relocate TCM)

Models:

2007-2011 Chevrolet Silverado
2007-2011 GMC Sierra
Equipped with Allison® A1000 Automatic Transmission (RPO MW7)

Attention:

Please refer to Article 1.2.2.12 - Non-General Motors Parts & Equipment and Original Equipment
Alterations of GM Service Policies and Procedure Manual for latest policy information on the use and
installation of aftermarket components.

This PI has been revised to remove the 2012 model year and add a Note before Step 6. Please discard PI0310B.
The following information may be helpful if the vehicle exhibits the symptoms described in this PI.

Condition/Concern
Some customers may comment that the transmission will intermittently hesitate, clunk, gets stuck in gear or in neutral, won't shift, or experience reduced torque
or range inhibit.
The technician may observe on a scan tool DTC P0880 and/or DTC U0101 set as Current or in History.
This condition may be caused by:

•

Resistance in the G102 ground connection on the side of the engine block.

•

During normal servicing, the OEM General Motors serpentine belt was replaced by an aftermarket serpentine belt.

•

An aftermarket serpentine belt was intentionally installed, due to dimension changes from added aftermarket equipment such as a second alternator or
clutch pump installed by an upfitter.

Certain brands of replacement aftermarket serpentine belts are made of compounds that will reduce the opportunity for audible belt noise, however these
compounds can generate significant amounts of electrostatic charge on their surface. This electrostatic charge can discharge and cause DTC P0880 and/or
DTC U0101 to set and be accompanied by any of the above symptoms.

Recommendation/Instructions
Important: DO NOT replace the transmission control module (TCM) until the root cause of the problem has been properly resolved. The TCM ONLY NEEDS
to be replaced if it has incurred permanent damage, such as hard failed codes, complete loss of communication or other erratic behavior that continues to exist
AFTER completing the following steps.
1.

Perform the Diagnostic System Check - Vehicle.

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2.

If DTC P0880 and/or U0101 are set as Current or in History, and/or the above symptoms are observed, proceed to Step 2.
If DTC P0880 and/or U0101 are not set as Current or in History, and/or the above symptoms are not observed, refer to > Transmission > Automatic
Transmission - Allison > Diagnostic Information and Procedures in SI.

Turn OFF the ignition.

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3.

Disconnect and inspect the G102 wire terminal and connection for looseness and corrosion. Clean any corrosion from the wire terminal and the surface
of the engine block with a wire brush.

4.

Apply dielectric grease to the wire terminal and engine block surface. Connect the G102 wire terminal and secure properly.

5.

Inspect the engine for an aftermarket serpentine belt due to service replacement or added aftermarket equipment from an upfitter.

⇒
⇒

If an aftermarket serpentine belt is installed on the original serpentine system, without added aftermarket equipment installed on the engine, replace
the serpentine belt with an OEM General Motors serpentine belt. Refer to Drive Belt Replacement in SI.
If an aftermarket serpentine belt is installed because of added aftermarket equipment installed on the engine, proceed to Step 6.

Important: DO NOT relocate the transmission control module (TCM) if aftermarket equipment HAS NOT been installed on the engine.
Relocate the TCM ONLY if an additional or longer accessory drive belt has been installed on the engine, resulting in the drive belt being closer to the
TCM.
Relocating the TCM on a vehicle that has not been modified, WILL NOT correct the DTCs and may result in a comeback.
Note: Early in the 2011 model year, the TCM wire harness was shortened and may prevent relocating the TCM. If the wire harness on a 2011 vehicle
is too short to relocate the TCM, the TCM should be replaced.
6.

Relocate the TCM (1) to the top of the UBEC cover and secure it using a heavy duty adhesive or Velcro® “hook and loop fastener”. DO NOT use push
pins as fasteners, they will compromise the water resistance of the UBEC cover.

Warranty Information
This repair is not covered under any GM Warranty provisions as the result of aftermarket equipment being installed.
Velcro® is a registered trademark of Velcro Industries B.V.
Allison® is a registered trademark of Allison Transmission, Inc.
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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