PIN AS 4992600 - Caterpillar

The Engine Control Module (ECM) uses vehicle speed information for the following features:
Cruise control
Fast idle control
Idle speed control
PTO operation
Vehicle speed limiting
Speedometer
Progressive shift
Idle shutdown
Operation of the air inlet heater
Secure idle theft deterrent
Trip data
Maintenance dataThere are three different methods that can be used to obtain the information for the ECM to use for calculating vehicle speed. The ECM can calculate vehicle speed by either of the following means:"Vehicle Speed Calibration" - The ECM monitors the signal from a vehicle speed sensor in pulses per kilometer (mile). The vehicle speed sensor is connected to the vehicle speed input circuit (terminals 32 and 33 of the ECM)."Vehicle Speed Cal (J1939-Trans)" - The ECM receives a message over the J1939 data link from the Transmission control module that represents revolutions per kilometer (mile) of the transmission output shaft."Vehicle Speed Cal (J1939-ABS)" - The ECM receives a message over the J1939 data link from the Anti-lock Brake System (ABS) that contains information about the wheel speed.Each of these methods require a specific calibration number to be programmed into the ECM to calculate vehicle speed.For the "Vehicle Speed Calibration" option that uses the vehicle speed sensor, the ECM must know the number of pulses that are produced by the vehicle speed sensor during each kilometer (mile) of travel by the vehicle. In order to find the number of pulses that are produced by the sensor, multiply the tire size by the axle ratio. Multiply the result of this calculation by the number of chopper teeth on the chopper wheel of the transmission output shaft.For the "Vehicle Speed Cal (J1939-Trans)" option, the ECM must know the number of times that the output shaft revolves per kilometer (mile) of travel by the vehicle. This can be calculated by one of the following methods:
Divide the pulses per kilometer (mile) of the sensor on the transmission output shaft by the number of teeth on the transmission output shaft.
Multiply the axle ratio by the number of revolutions per kilometer (mile) of the tire.For the "Vehicle Speed Cal (J1939-ABS)" option, the ECM must be programmed with a calibration number. This number is calculated by dividing the actual tire revolutions per kilometer (mile) by the tire revolutions per kilometer (mile) that is programmed into the ABS system.The ECM calculates vehicle speed by converting the vehicle speed signal to kilometers per hour (km/h) or miles per hour (mph). The conversion factor is customer programmable. The conversion factor must be entered as a configuration parameter in pulses per km (PPKM) or pulses per mile (PPM).The variable for the tire revolution is affected if the tire size or the tire type is changed on the rear axles of the truck. If the bias ply tires are replaced with radial tires, be sure to recalibrate the ECM. Also, if you change the brand of the tire that is used on the vehicle, the variable for the tire revolution should be checked.These changes will cause variations between the actual vehicle speed and the vehicle speed that is