UPDATE-DRIVEABILITY & EMISSION CODE 62 FACING PAGE AND CHART

VEHICLES AFFECTED: 1990 "N" 2.3L (VIN D)

* This bulletin has been revised to include proper location of second gear switch, labeling of ECM connector and to clarify Code 62 Chart.

This bulletin serves to update the Code 62 chart and facing page in Section 6E3 "Driveability And Emissions" in the 1990 Service Manuals with 2.3L (VIN D) "N-Car" applications. (Chart and facing page attached)

TRANSMISSION GEAR SWITCHES CIRCUIT 2.3L (VIN D & A) "N" CARLINE (PORT)

Circuit Description:

Code 62 diagnostic is used to check the 2nd and 3rd gear switch inputs to the ECM. Transmission gear input signals to the ECM are determined as follows:

1st gear = 2nd gear switch closed (also P/N & R) 3rd gear switch closed 2nd gear = 2nd gear switch open 3rd gear switch closed 3rd gear = 2nd gear switch open 3rd gear switch open.

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

Code 62 will set if any of the following conditions are met for approximately 17 seconds:

In "PARK" or "NEUTRAL" and 2nd or 3rd gear indicated.

Vehicle speed less than approximately 5 mph and 2nd or 3rd gear indicated.

First or second gear indicated, less than approx, 3000 rpm, not in P/N, and VSS greater than 50 mph.

Vehicle at operating temperature.

1. Step one checks for an open or grounded circuit between transmission connector and ECM. Since the ECM terminals are normally high, B + should be indicated at both terminals with the connector removed.

2. The DVM should measure near B+ because the 2nd and 3rd gear switches should provide continuity to ground.

3. The third step checks to see if the transmission switches function normally. In third gear both switches should have changed from their original 1st gear state.

Diagnostic Aids:

Clear codes and recheck for Code 62. If code resets, check all harness connections, VSS, rpm, P/N circuits prior to replacing an ECM. Transmission starting in 2nd or 3rd gear or a sticky 2nd gear switch can also cause Code 62.

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.