DIAGNOSIS REPEATED ECM REPLACE MISADJUSTED ISC MOTOR

GR. 6C DFI CODE 30 MAY BE CAUSED BY MISADJUSTED ISC MOTOR EARLY FIELD EXPERIENCE INDICATES THAT THE MOST COMMON CAUSE FOR SETTING A CODE 30 ON 1981 DFI ENGINES IS A MISADJUSTED ISC MOTOR. MISADJUSTMENT IS ALSO THE CAUSE OF A "RATCHETING" NOISE THAT MAY BE HEARD (OR FELT IN THE ACCELERATOR PEDAL) WHEN THE KEY IS TURNED TO THE "ON" POSITION. IF AFTER ADJUSTING THE TPS, MINIMUM AIR RATE AND ISC, PER SERVICEMAN BULLETIN 81-5, THE CONDITION PERSISTS, READJUST THE ISC MOTOR TO THE HIGH END OF THE IDLE SPEED SPECIFICATION (1700 RPM). SEE STEP 7 IN ISC MOTOR ADJUSTMENT SECTION, SERVICEMAN BULLETIN 81-5. DO NOT REPLACE ISC MOTORS WHEN PROPER ADJUSTMENTS WILL CORRECT THE CONDITION.

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.