RING-BACKUP 4I3615 - Caterpillar

System Operation Description: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:
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). This is the "Vehicle Speed Calibration" option.
The ECM receives a message over the J1939 data link from the transmission ECU that indicates revolutions per kilometer (mile) of the transmission output shaft. This is the "Vehicle Speed Cal (J1939-Trans)" option.
The ECM receives a message over the J1939 data link from the Anti-lock Brake System (ABS) that contains information about the wheel speed. This is the "Vehicle Speed Cal (J1939-ABS)" option.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 number that was obtained in the previous calculation by the number of teeth on the output shaft that is used by the sensor to obtain the pulses.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 know a calibration number. The 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.The ECM calculates vehicle speed by converting the vehicle speed signal to kilometers per hour (km/h) or to miles per hour (mph). The conversion factor is customer programmable and the conversion factor is stored in pulses per km (PPKM) or pulses per mile (PPM).The variable for the tire revolution could be affected by changing from bias ply tires to radial tires and vice versa. Also, changing to radial tires that have a low profile could affect the variable for the tire revolution. This result may change the actual vehicle speed which could result in performance complaints or in complaints about fuel consumption. If the tire configuration has been changed, determine the