Important Information

Subject: Allison LCT1000 Transmission - Tech 2 Operation Aids, DTC P0700 - kw automatic GMT800 hard harsh inoperative intermittent leak no operation performance slip SRTA PI01978 - (04/14/2004)

Models: (01-02 Chevrolet Silverado) and (01-02 GMC Sierra)

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

Condition/Concern:
When using the Tech 2 on 2001 and 2002 GMT800 Trucks equipped with the Allison LCT1000 Transmission, you may experience difficulty in locating the proper vehicle build and TCM DTCs. It is possible that the wrong vehicle options were picked when setting up the Tech 2 on the vehicle, not allowing access to the TCM DTCs.

Recommendation/Instructions:
The following aids will allow proper operation of the Tech 2 on the Allison LCT1000 (This information was correct as of 2/27/01.) Select as follows:

1) 2001

Light Truck, MPV, Incomplete

F0: Powertrain

(1) 6.6L LB7 Diesel or (G) 8.1L L18 (Note: Do not select (G) 8.1L L18 3500HD only The 3500HD is a GMT400 vehicle and not available with an Allison LCT1000)

5 Speed Automatic

In order to obtain DTCs from the transmission the following steps must be followed.

F0: Diagnostic Trouble Codes (DTC)

F1: DTC's (Engine)

F2: DTC's (Transmission)

Many dealers have reported a DTC of P0700. The MIL request circuit signals the ECM that the TCM is requesting MIL illumination. Upon further investigation by checking TCM DTCs, additional codes are discovered.

Please follow this diagnosis 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. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

NOTE: 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.