Payload weight measurement is a function of the suspension cylinder pressure sensors. Certain conditions could affect the accuracy of the Truck Payload Measurement System (TPMS) when the truck is loaded. Some of these conditions are listed as follow:
- A truck is loaded on a sloped surface that is greater than 5%. Accuracy will become progressively worse as the slope becomes greater.
Note: Refer to System Operation, "Payload Management Guidelines" for proper loading guidelines.
- A suspension cylinder is not properly charged. The suspension cylinders may not cause an event even if the charge is incorrect. However, the weighing accuracy will be affected.
Note: Refer to Special Instruction, SEHS9411, "Servicing the Suspension Cylinders for Off-Highway Trucks" for information on servicing the suspension cylinders.
- Pushing down on the load with the loading tool during the loading process (packing the load)
- Actuating the body raise lever during loading
- A failure to perform payload calibration after replacing components in the TPMS.
- A failure to perform payload calibration after any substantial changes to the empty weight of the truck. Refueling does not require payload calibration.
- Using a conveyor or a continuous feed system for loading
- Failures in the TPMS may cause the payload weight to become inaccurate. Diagnostic events will be shown in the "event list".
- The incorrect VIMS 3G onboard software is installed.
- The load is placed in the body, too far from the center of the marker.
- The payload configuration is set incorrectly.
Note: The accuracy of the TPMS is not affected if the first load is placed into the truck before the truck has stopped completely. The truck can also be repositioned during loading.
If the accuracy of the payload measurement is suspect, confirm the list of items that follow:
- The VIMS ECM have the correct software and the most recent revision.
- No service work has been performed on the payload system that may have created the reported diagnostic.
- The Payload system is configured correctly for the model of the truck. Refer to Testing and Adjusting, "Payload System - Configure".
- The payload system has been calibrated. Refer to Testing and Adjusting, "Payload System - Calibrate".
- The suspension cylinders are not topping out or bottoming out due to an incorrect charge pressure. Refer to Special Instruction, SEHS9411, "Servicing the Suspension Cylinders for Off-Highway Trucks".
The reweigh process may not be triggered if the "Second Gear Reweigh" feature and the "Second Gear Start" feature are both enabled.
The accuracy of the reweigh process will be affected if the reweigh feature is changed from the default.
Note: Perform an accuracy study when changing the reweigh feature.