Description:
By setting the Vehicle Speed Input parameter to the J1939-ABS option, the ECM will be calibrated to receive vehicle speed information using Antilock Brake System (ABS) wheel speed over the J1939 datalink. The Vehicle Speed Cal (J1939-ABS) parameter value represents the ratio of actual tire revolutions per mile divided by assumed ABS tire revolutions per mile, and is used with the wheel speed signal (received over the J1939 datalink) to calculate vehicle speed.
It is important to note that if this calibration method is to be used, the ABS must be able to support the J1939 High Resolution Wheel Speed Broadcast Message, which provides wheel speed from the two rear wheels. In addition to the wheel speed, the ABS will also transmit the actual revolutions per mile, which should be divided by the assumed ABS tire revolutions per mile to obtain the Vehicle Speed Cal (J1939-ABS) parameter.
OEM Responsibilities:
• Determine if the ABS can support the required message protocol mentioned above.
• It is recommended that the OEM program the Vehicle Speed Calibration parameter.
Parameter Calculation Method:
Vehicle Speed Cal =
Actual Tire Revolutions Per Mile
Assumed ABS Tire Revolutions Per Mile
Available:
All electronically controlled on-highway engines covered in this handbook
Range:
