For 1990-2009 cars

# CODE 34 MASS AIR FLOW SENSOR VOLTAGE LOW

1985 "F" CAR WITH LB9 ENGINE (ENGINE CODE F)

Some "F" cars with the port fuel engine may experience complaints of check engine light and poor driveability. It has been determined that Mass Air Flow Sensors have been replaced and in many cases have not corrected the complaint.

If this condition occurs and a Code 34 is found stored in the ECM,the following steps should be taken.

1. Check engine for vacuum leaks.

2. Set minimum idle speed to 500 RPM as described in the 1985 Shop Manual. (Page 6E3-148)

3. Perform diagnostic check for Code 34 found in your 1985 Shop Manual. (Page 6E3-101)

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.