TEMPORARY DIP SAG WITH WARM ENGINE. Chevrolet S10 Pickup

SUBJECT: TEMPORARY DIP SAG WITH WARM ENGINE (NEW 'FLASH' CALIBRATIONS)

MODELS: 1996 CHEVROLET AND GMC TRUCK S/T MODELS WITH 4.3L V6 ENGINE (VINS W, X - RPOS L35, LF6)

CONDITION:

SOME OWNERS MAY COMMENT ON A DRIVEABILITY CONDITION KNOWN AS TEMPORARY DIP OR SAG ON A WARM RE-STARTED ENGINE, AFTER APPROXIMATELY A ONE HOUR SOAK.

THE CONDITION DIP OR SAG IS DESCRIBED AS A LACK OF ENGINE RESPONSE AT A PARTICULAR THROTTLE POSITION. THE ENGINE MAY STUMBLE AND PERFORM POORLY.

THIS CONDITION MAY BE NOTICEABLE AT A STEADY, LIGHT THROTTLE OPERATION AND BE NOTICEABLE FOR 30 SECONDS TO A MINUTE, AFTER WHICH TIME THE CONDITION COMPLETELY DISAPPEARS.

CAUSE:

THE ENGINE IS RUNNING IN A CLOSED-LOOP STATUS WHEN THE OXYGEN SENSORS ARE NOT FULLY OPERATIONAL.

CORRECTION:

NEW 'FLASH' CALIBRATIONS WERE RELEASED IN PRODUCTION VEHICLES DURING SEPTEMBER, 1995.

VEHICLES EXHIBITING THIS SPECIFIC DRIVEABILITY CONCERN SHOULD BE UPDATED WITH THE NEW CALIBRATIONS AS FOLLOWS:

FOR FEDERAL AND CALIFORNIA VEHICLES

MODEL - BODY STYLE ENGINE TRANS. EMISSION OLD CAL. NEW CAL.

4 WD, 2 L35 AUTO NATIONWIDE 16227487 16232320 AND 4 DR. UNLEADED UTILITY FUEL

2 AND 4 L35 MAN UNLEADED 16227490 16232324 WD, ALL FUEL BODIES

2 WD ALL L35 AUTO UNLEADED 16227493 16232327 BODIES, FUEL 4 WD STD. AND EXT. CAB P.U.

2 WD ALL LF6 AUTO UNLEADED 16227496 16232330 BODIES FUEL

4 WD ALL LF6 AUTO UNLEADED 16227498 16232332 BODIES FUEL

2 WD ALL LF6 MAN UNLEADED 16227500 16232334 BODIES FUEL

4 WD ALL LF6 MAN UNLEADED 16227502 16232336 BODIES FUEL

FOR CANADIAN VEHICLES

MODEL/ BODY STYLE ENGINE TRANS. EMISSION OLD CAL. NEW CAL.

4 WD, 2 L35 AUTO UNLEADED 16227488 16232321 AND DR. 4 FUEL UTILITIES

2 AND 4 L35 MAN UNLEADED 16227491 16232325 WD ALL FUEL BODIES

2 WD ALL L35 AUTO UNLEADED 16227494 16232328 BODIES, FUEL STD. AND EXT. CAB P.U.

2 WD ALL LF6 AUTO UNLEADED 16227497 16232331 BODIES FUEL

4 WD ALL LF6 AUTO UNLEADED 16227499 16232333 BODIES FUEL

2 WD ALL LF6 MAN UNLEADED 16227501 16232335 BODIES FUEL

4 WD ALL LF6 MAN UNLEADED 16227503 16232337 BODIES FUEL

FOR EXPORT VEHICLES

MODEL/ BODY STYLE ENGINE TRANS. EMISSION OLD CAL. NEW CAL.

4 WD, 2 L35 AUTO UNLEADED 16227489 16232322 2 AND 4 DR. FUEL UTILITY

2 AND 4 WD L35 MAN UNLEADED 16227492 16232326 ALL BODIES FUEL

2 WD ALL L35 AUTO UNLEADED 16227495 16232329 BODIES; FUEL 4 WD STD. AND EXT. CAB P.U.

4 WD, 2 L35 AUTO EUROPEAN 16227512 16232323 AND 4 DR. AND JAPAN UTILITY UNLEADED FUEL

STANDARD DIAGNOSTIC PROCEDURES AND TROUBLE SHOOTING FLOW CHARTS SHOULD BE USED WHEN SERVICING THE ABOVE VEHICLES WITH THE NEW CALIBRATIONS.

SERVICE INFORMATION THE ABOVE SERVICE 'FLASH' CALIBRATIONS ARE AVAILABLE STARTING WITH THE OCTOBER, 1995 CD ROM. THESE CALIBRATIONS ARE NOT AVAILABLE FROM GMSPO.

WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION LABOR TIME --------------- ---------- J-6355 0.3 HR

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.