SERVICE MANUAL UPDATE SEC. 6EA CONNECTOR END VIEW CHART

Subject: ADDITIONAL TYPICAL VOLTAGES AND ECM CONNECTOR END VIEW CHARTS

Models Affected: 1990-1991 LUMINA AND CORVETTE

This bulletin updates the following engines and carlines:

1990-1991 2.5L (VIN R) "W" CARLINE 1990-1991 3.1L (VIN T) "W" CARLINE 1990-1991 3.4L (VIN X) "W" CARLINE 1990-1991 5.7L (VIN J) "Y" CARLINE 1990-1991 5.7L (VIN 8) "Y" CARLINE

Service Technicians have commented about the inability to read typical voltages in these Electronic Control Module (ECM) Connector End View charts. These charts are located in Service Manual Section "6E-A", "Driveability And Emissions." This condition has led to development of new charts. Vehicles equipped with the ECM in the engine compartment require the use of sealed electrical connections. The practice of "backprobing," piercing insulation, or otherwise breaching the integrity of circuits for diagnostic purposes is strongly not recommended.

The attached charts may be used in conjunction with the T-100 *Yellow Breakout Box (48921) to obtain voltage values for each circuit listed. Furthermore, if the voltage is found to be abnormal, the technician may reference the appropriate section, chart, or figure within the service manual to enhance further diagnosis of the circuit in question.

* "We believe T-100 equipment to be reliable. There may be additional manufacturers of such equipment. General Motors does not endorse, indicate any preference for, or assume responsibility for the products or equipment from those firms or for any such items which may be available from other sources."

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.