Incorrect Calibration (C & K Series)

Check rear axle ratio and rear tire size if the same as factory identification label on glove box door. If rear axle ratio and tire size are same as factory equipped, check vehicle speed sensor circuit. See VEHICLE SPEED SENSOR & DIGITAL RATIO ADAPTER CONTROLLER .
If rear axle ratio and/or tire size are different from factory specifications, check digital ratio adapter calibration clip on rear of instrument cluster for proper calibration pins to be removed. See SPEEDOMETER CALIBRATION ADJUSTMENT .
Check for brake Code 9 with inoperative speedometer/odometer or check for ECM Code 24 with correctly operating speedometer/odometer. See TESTS W/CODES TBI article in the ENGINE PERFORMANCE section and appropriate ANTI-LOCK BRAKES article in the BRAKES section for trouble code diagnosis. If ECM Code 24 is set and speedometer/odometer operates, check vehicle speed sensor buffer output. See BUFFER OUTPUT (C & K SERIES) TESTING .
If brake Code 9 is set and speedometer/odometer are inoperative, check vehicle speed sensor buffer power input. See BUFFER POWER DIAGNOSIS. Also check vehicle speed sensor circuit. See VEHICLE SPEED SENSOR & DIGITAL RATIO ADAPTER CONTROLLER .