SERVICE MANUAL UPDATE SEC. 7A TRANSMISSION DIAGNOSIS CHARTS

Subject: AUTOMATIC TRANSMISSION DIAGNOSIS CHARTS UPDATED

Model and Year: 1991 C/K, R/V, P AND G TRUCKS WITH 4L80-E/4L80-EHD AUTOMATIC TRANSMISSION

BULLETIN COVERS:

HYDRA-MATIC 4L80-E/4L80-EHD Transmission updates occurring after Service Manual printing.

LIGHT DUTY TRUCK SERVICE MANUAL UPDATES:

Automatic Transmission / Diagnosis Information: Range Reference Chart has been revised. (Figure 1) Wiring Diagram has been revised. (Figure 2)

Remove Notice under Torque Converter Clutch (TCC) Diagnosis: Notice says: Do not bench test the TCC Solenoid using an automotive type battery. Accidentally crossed wires will damage the internal diode of the Solenoid. (This notice does not apply to the 4L80-E Transmission.)

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those 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 a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.