HT4100 PROM USAGE HI ALT IMPROVED TCC AND IDLE SPEED

A REVISED PROM CALIBRATION HAS BEEN RELEASED FOR 1982 HT4100 EQUIPPED VEHICLES. THESE SECOND GENERATION PROM'S PROVIDE MINOR MODIFICATIONS TO THE DFI SYSTEM'S FUEL CALIBRATION, IDLE SPEED CONTROL AND TORQUE CONVERTER CLUTCH (TCC) ENGAGEMENT CONTROL. TWO MODIFICATIONS TO THE TCC ENGAGEMENT CONTROL ARE: 1.TCC ENGAGEMENT SPEED HAS BEEN RAISED FROM 48 MPH TO 53 MPH ON SECOND GENERATION E/K CARS; FIRST GENERATION E/K CARS AND ALL C-CARS ALLOW TCC ENGAGEMENT AT 48 MPH. 2.TCC BAROMETRIC DISABLE WILL OCCUR BELOW 92 KPA (REFER TO ENGINE DATA DISPLAY PARAMETER .0.3, BARO VALUE) ON VEHICLES WITH SECOND GENERATION FEDERAL PROM CALIBRATION. SECOND GENERATION CALIFORNIA AND HIGH ALTITUDE PROM CALIBRATIONS WILL DISABLE TCC BELOW 79 KPA. ALL FIRST GENERATION PROM CALIBRATIONS WILL DISABLE TCC BELOW 81 KPA. THESE CHANGES SHOULD ONLY BE DETECTED WHEN DRIVING IN HIGH ALTITUDE AREAS. WHEN SERVICING 1982 HT4100 EQUIPPED VEHICLES, REFER TO FIGURE 1 ON THE REVERSE SIDE FOR UPDATED PROM SERVICE PARTS INFORMATION. (SEE BULLETIN FOR FIGURE 1) FIRST AND SECOND GENERATION HIGH ALTITUDE PROM'S MUST NOT BE INTERCHANGED. THE SECOND GENERATION HIGH ALTITUDE PROM CALIBRATION WAS RELEASED CONCURRENT WITH AN INCREASED AXLE RATIO FOR HIGH ALTITUDE USE. BECAUSE OF THIS AXLE RATIO CHANGE, A CODE 39 (TCC ENGAGEMENT) MAY BE SET WITH IMPROPER PROM USAGE DUE TO THE EXPECTED VEHICLE SPEED TO ENGINE RPM RELATIONSHIP NOT BEING MET.

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