NO UPSHIFT SECOND GEAR ONLY AFTER COLD START. GMC Truck GMC MD Steel Tilt 67.9" 1994

SUBJECT: NO UPSHIFT, SECOND GEAR ONLY AFTER COLD START, DTC 87 (REPLACE PROM)

MODELS: 1994-95 CHEVROLET TILTMASTER AND GMC FORWARD W4 MODELS WITH 4L80-E AUTOMATIC TRANSMISSION

CONDITION:

SOME OWNERS MAY REPORT THE TRANSMISSION WILL NOT UPSHIFT AFTER A COLD START AND STAYS IN SECOND GEAR.

CAUSE:

THE PCM SHIFT COMMAND TO THIRD OR FOURTH GEAR IS TAKING LONGER THAN TWO SECONDS WITH A MINIMUM 25% THROTTLE POSITION SENSOR READING. THIS CAN CAUSE DTC 87 TO BE SET.

CORRECTION:

FOLLOW THE STRATEGY BASED DIAGNOSTICS AND PUBLISHED PROCEDURES FOR THE SYMPTOM. IF NORMAL DIAGNOSIS DOES NOT RESOLVE THE CONDITION AND DTC 87 SETS ONLY AFTER A COLD START, REPLACE THE PROM WITH ONE OF THE P/N'S LISTED BELOW FOLLOWING THE PROCEDURE DESCRIBED IN SECTION 6E OF THE SERVICE MANUAL. THE NEW PROM RAISES THE DTC SHIFT TIME PARAMETER TO FOUR SECONDS AND THE CODE ENABLING TEMPERATURE TO 68 DEGREES F (20 C).

PARTS INFORMATION

P/N DESCRIPTION QTY 16248371 E-PROM, PCM (94 MY) 1 16244962 E-PROM, PCM (95 MY) 1

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO

WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OP DESCRIPTION LABOR TIME J6364 PROM, PCM - REPLACE USE PUBLISHED LABOR OPERATION TIME

IMPORTANT: LABOR OPERATION IS CODED TO BASE VEHICLE COVERAGE IN THE WARRANTY SYSTEM.

FIGURES: 00 ATTACHMENTS: 00

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.