SMU - SECTION 6E3 - DRIVEABILITY & EMISSIONS

SUBJECT: SERVICE MANUAL UPDATE-SECTION 6E3-DRIVEABILITY AND EMISSIONS- REVISED CHART A-3 - ENGINE CRANKS BUT WILL NOT RUN

MODELS: 1988-95 BUICK SKYLARK 1990-94 CHEVROLET BERETTA 1995 CHEVROLET CAVALIER 1992-95 OLDSMOBILE ACHIEVA 1987 OLDSMOBILE CALAIS 1988-91 OLDSMOBILE CUTLASS CALAIS 1990-91 OLDSMOBILE CUTLASS SUPREME 1988-95 PONTIAC GRAND AM 1990-91 PONTIAC GRAND PRIX 1995 PONTIAC SUNFIRE WITH 2.3L ENGINE (VINS A, D, 3 - RPOS LG0, LD2, L40)

THIS BULLETIN IS BEING ISSUED TO REVISE SECTION 6E3 OF THE 1987-95 2.3L ENGINE APPLICATION SERVICE MANUALS. THE CHART A-3 ENGINE CRANKS BUT WILL NOT RUN CHART HAS BEEN REVISED WHEN CHECKING FOR THE CRANK SENSOR'S OUTPUT VOLTAGE.

THE TECHNICIAN IS DIRECTED TO READ THE AC VOLTAGE OUTPUT OF THE SENSOR AT THE IGNITION MODULE CONNECTOR WHILE CRANKING THE ENGINE. IF THE VOLTAGE IS ABOVE A SPECIFIED VALUE, THE SENSOR IS CONSIDERED OK. IT HAS BEEN FOUND THAT A FAULTY SENSOR MAY STILL BE ABLE TO GENERATE AN AC VOLTAGE HIGHER THAN SPECIFIED IN THE DIAGNOSTIC CHART, CAUSING MIS-DIAGNOSIS OF THE IGNITION MODULE.

A NORMAL SENSOR GENERATES AN AC VOLTAGE OF APPROXIMATELY 1100MV TO 1300MV. AN OK BUT HIGH RESISTANCE SENSOR THAT MAY NOT CAUSE A "CRANKS BUT WILL NOT RUN" CONDITION MAY GENERATE A VOLTAGE AS LOW AS 500MV - 600MV.

AN OPEN SENSOR MAY GENERATE AN AC VOLTAGE OF HIGHER THAN THE SPECIFIED VOLTAGE IN THE STEP AND CAUSE A NO START CONDITION.

THE FOLLOWING REVISIONS SHOULD BE MADE TO THE SPECIFIED STEPS OF CHART A-3 FOR THE 1987-95 SERVICE MANUALS WITH OBD 1 DIAGNOSTIC SYSTEMS.

1987-92 SERVICE MANUALS - STEP 13 * CONNECT A DVM BETWEEN TERMINALS "B" AND "C" OF IDI MODULE HARNESS. * MEASURE THE COMBINED RESISTANCE VALUE OF THE CRANK SENSOR AND CRANK SENSOR HARNESS. * RESISTANCE SHOULD BE BETWEEN 500 AND 900 OHMS. * CRANK THE ENGINE AND OBSERVE VOLTAGE (AC SCALE). * READING SHOULD BE GREATER THAN 200 MV. ARE BOTH THE DVM READINGS WITHIN THE GIVEN VALUES?

1993-95 SERVICE MANUALS - STEP 11 * CONNECT A DVM BETWEEN TERMINALS "F" AND "J" OF THE ELECTRONIC ICM HARNESS (OR ICM 11 PIN HARNESS CONNECTOR). * MEASURE THE COMBINED RESISTANCE VALUE OF THE CRANK SENSOR AND CRANK SENSOR HARNESS. * RESISTANCE SHOULD BE BETWEEN 500 AND 900 OHMS. * CRANK THE ENGINE AND OBSERVE VOLTAGE (AC SCALE). * READING SHOULD BE GREATER THAN 200 MV. ARE BOTH DVM READINGS WITHIN THE GIVEN VALUES?

1995 J SERIES UPDATE MANUAL HAS BEEN REVISED AS ATTACHED. INFORMATION NOT INCLUDED WITH THIS ATTACHMENT HAS NOT BEEN REVISED.

PLEASE MAKE A NOTE OF THESE REVISIONS IN YOUR SERVICE MANUALS.

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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.

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