For 1990-2009 cars

# UNSTABLE ENGINE IDLE (REPROGRAM PCM)

#### SUBJECT: UNSTABLE ENGINE IDLE (REPROGRAM PCM)

#### MODELS: 1997 CHEVROLET MALIBU 1997 OLDSMOBILE CUTLASS WITH 3100 V6 ENGINE (VIN M - RPO L82)

#### CONDITION:

SOME OWNERS MAY EXPERIENCE AN UNSTABLE ENGINE IDLE. THE CONTROLLED ENGINE IDLE MAY VARY APPROXIMATELY 50 RPM FROM DESIRED IDLE. THIS TYPICALLY OCCURS DURING AN EXTENDED IDLE PERIOD BEYOND 30 SECONDS WITH THE TRANSMISSION IN PARK OR NEUTRAL AND THE AIR CONDITIONING TURNED OFF.

#### CAUSE:

THE PRE CONVERTER HEATED OXYGEN SENSOR (HO2S1) VOLTAGE OUTPUT IS DRIVEN LOW AND HOLDS THERE (LEAN). THE POST CONVERTER HEATED OXYGEN SENSOR (HO2S2) VOLTAGE OUTPUT WILL HOLD THEN AT A HIGH VOLTAGE (RICH). THIS CAN DRIVE ONE SENSOR TO CANCEL OUT THE OTHER THUS NOT ALLOWING FUEL TRIM OR THE POST CONVERTER HEATED OXYGEN SENSOR CAN TAKE OVER FUEL TRIM CONTROL. IF THE POST CONVERTER HEATED OXYGEN TAKES OVER FUEL TRIM CONTROL, THE SYSTEM THINKS IT IS RUNNING RICH AND THE LONG TERM FUEL TRIM WILL MAKE ADJUSTMENTS TO LEAN THE SYSTEM. EITHER OF THESE CONDITIONS WILL CAUSE A ROLLING OR HUNTING IDLE.

#### CORRECTION:

CHECK THE CALIBRATION IDENTIFICATION NUMBER UTILIZING A SCAN TOOL DEVICE. RE-FLASH WITH THE UPDATED CALIBRATION IF THE CURRENT CALIBRATION IS NOT ONE LISTED IN THIS BULLETIN. IF THE VEHICLE ALREADY HAS THE MOST RECENT CALIBRATION, THEN REFER TO THE APPROPRIATE SERVICE REPAIR MANUAL TO DIAGNOSE AND REPAIR. TEST DRIVE THE VEHICLE AFTER REPAIR TO ENSURE THAT THE CONDITION HAS BEEN CORRECTED. THE NEW CALIBRATIONS ARE AVAILABLE FROM THE GM SERVICE TECHNOLOGY GROUP STARTING WITH CD NUMBER 12 FOR 1997.

#### IMPORTANT: THERE ARE THREE METHODS FOR PROGRAMMING A PCM:

1. DIRECT PROGRAMMING. THE VEHICLE IS DIRECTLY CONNECTED VIA THE DATA LINK CONNECTOR (DLC) ON THE DEALERS/RETAILERS TECHLINE EQUIPMENT. (T-20 PLUS, T-50 AND T-60 ONLY) VEHICLE MUST BE PRESENT.

2. REMOTE PROGRAMMING. THE NEW PROGRAM IS DOWNLOADED INTO THE DEALERS/RETAILERS SCAN TOOL AND THEN DOWNLOADED INTO THE VEHICLE FROM THE SCAN TOOL VIA THE DLC. TECH 2 REQUIRED. VEHICLE MUST BE PRESENT.

3. OFF-CAR PROGRAMMING. A PCM MAY BE PROGRAMMED WHILE REMOVED FROM THE VEHICLE BY USING THE OFF-BOARD PROGRAMMING ADAPTER (OBPA), P/N 41207- B. THIS ADAPTER CAN BE CONNECTED TO EITHER THE TECHLINE TERMINAL FOR DIRECT PROGRAMMING OR THE SCAN TOOL FOR REMOTE PROGRAMMING. NOT NECESSARY FOR THE VEHICLE TO BE PRESENT.

REFER TO THE APPROPRIATE SERVICE MANUAL OR TECHLINE INFORMATION FOR MORE DETAILED INSTRUCTIONS.

PARTS INFORMATION

PART NUMBER CARLINE EMISSIONS

16266904 MALIBU, CUTLASS USA NATIONWIDE

16266914 MALIBU, CUTLASS CANADIAN/UNLEADED EXPORT

16266924 MALIBU LEADED EXPORT

#### IMPORTANT: DO NOT ATTEMPT TO ORDER THE CALIBRATIONS FROM GMSPO. THE CALIBRATIONS ARE PROGRAMMED INTO THE VEHICLE'S PCM VIA A TECHLINE TOOL DEVICE.

WARRANTY INFORMATION

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION DESCRIPTION LABOR OPERATION TIME J6355 ON-CAR PROM USE PUBLISHED LABOR REPROGRAMMING OPERATION TIME. FLASH E PROM

J6352 OFF-CAR PROM USE PUBLISHED LABOR REPROGRAMMING FLASH E OPERATION TIME. PROM

FIGURES: 0 ATTACHMENTS: 0

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.

COPYRIGHT 1997. GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.