Description:
By setting the Vehicle Speed Input parameter to the J1939-Trans option, the ECM will be calibrated to receive vehicle speed information over the J1939 datalink. The Vehicle Speed Cal (J1939-Trans) parameter value represents the Transmission Output Shaft revolutions per mile, and is used with the output shaft speed signal (received over the J1939 datalink) to calculate vehicle speed.
When the ECM is configured to receive Vehicle Speed information from an Electronic Transmission Control Unit via the J1939 datalink, the attached transmission must be capable of supporting the J1939 ETC1 Broadcast Message that provides the transmission output shaft speed.
OEM Responsibilities:
• Determine if the transmission is capable of supporting the required ETC1 message protocol.
• Determine the parameter value to be programmed for a given chassis by one of the methods listed below.
Parameter Calculation Methods:
Method 1
Vehicle Speed Cal (J1939-Trans) =
Transmission Output Shaft revolutions per mile
Method 2
Vehicle Speed Cal (J1939-Trans) =
Transmission Speed Sensor pulse per mile
Number of teeth on the output shaft chopper wheel
Method 3
Vehicle Speed Cal (J1939-Trans) =
Tire revolutions per mile x Axle ratio
Available:
All electronically controlled on-highway engines covered in this handbook
Range:
