SERVICE MANUAL UPDATE-SEC.6E3 REVISED CHART C-8B

Model and Year: 1990 STORM WITH 1.6L (VIN CODE 5) ENGINE

This bulletin serves to revise the Chart C-8B facing page on Page 6E3-C8-40 in "Driveability And Emissions" Section 6E3 in the 1990 Geo Storm 1.6L (VIN 5 and 6) "R" Carline (Port) Service Manual.

The attached page reflects the correct shift light diagram and replaces the existing page in the 1990 Geo Storm Service Manual.

CHART C-8B MANUAL TRANSAXLE (M/T) SHIFT LIGHT CHECK 1.6L SOHC (VIN 6) & 1.6L DOHC (VIN 5) "R" CARLINE (PORT)

Circuit Description:

The shift light indicates the best transaxle shift point for maximum fuel economy. The light is controlled by the ECM and is turned "ON" by grounding the ORN/BLU wire. The ECM uses information from the following inputs to control the shift light:

The ECM uses information from the following inputs to control the shift light:

CTS TPS VSS RPM

The ECM uses the measured rpm and the vehicle speed to calculate what gear the vehicle is in. It's this calculation that determines when the shift light should be turned "ON."

Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. This should not turn "ON" the shift light. If the light is "ON," there is a short to ground in ORN/BLU wire or a fault in the ECM.

2. This checks the shift light circuit up to the ECM connector. If the shift light illuminates, then the ECM connector is faulty or the ECM does not have the ability to ground the circuit.

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.