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Vehicle Speed Parameters for On-Highway Trucks (Caterpillar Engines)

VSL Protection (PTO Operation)

Figure 1.1 - Vehicle Speed Signal Error (SPN 84 - FMI 10)
0084-10 Vehicle Speed Signal Rate of Change (36)
PID 0084 FMI 10 (SPN84 FMI10)

Conditions Which Generate This Code:
The ECM detects the following conditions:
  • The vehicle speed signal changes more than 5 MPH on eight consecutive readings in three seconds.
  • The engine speed is greater than the programmed "VSL Protection" minus 100 rpm.
  • The "VSL Protection" parameter is programmed to a value that is less than 2120 rpm.
Note: If the ABS is the source of the vehicle speed, the ABS must not be active.

System Response:
"DIAG" will be displayed next to the status for "Vehicle Speed" on the electronic service tool. The check engine lamp will illuminate.

Possible Performance Effect:
Engine rpm is limited to the programmed "VSL Protection" for eight seconds.


#Vehicle Speed Parameters
Note: Need the "Factory Passwords" to make setting: Vehicle Speed Calibration, Vehicle Speed Limit, and VSL Protection. Read More: Factory Passwords on Caterpillar ET Software.
Figure 1.2 - Vehicle Speed Parameters (Config Tool)

1). Vehicle Speed Calibration
The "Vehicle Speed Calibration" is the value that is used by the Engine Control Module (ECM) in order to translate the vehicle speed signal into kilometers per hour (miles per hour). This parameter is programmed in pulses per kilometer (PPKM) or pulses per mile (PPM). This parameter must be programmed. If the "Vehicle Speed Calibration" parameter is not programmed, 253-02 Check Customer or System Parameters will be active. This parameter affects the cruise control and the ECM speedometer signal. Also, this parameter can affect the PTO operation, extended idle and trip totals.
  • Minimum: 2485 PPKM (4000 PPM)
  • Maximum: 93226 PPKM (150000 PPM)
  • Default: 8696 PPKM (14000 PPM)

2). Vehicle Speed Cal (J1939-Trans)
The "Vehicle Speed Cal (J1939-Trans)" is used when the ECM is configured to use the speed of the transmission output shaft in order to calculate vehicle speed. The "Vehicle Speed Input" parameter must be programmed to "Vehicle Speed Cal J1939-Trans". This value represents the revolution of the transmission output shaft as revolutions per kilometer (revolutions per mile). This parameter must be programmed. If this parameter is not programmed, 253-02 Check Customer or System Parameters will be active. This parameter affects the cruise control and the ECM speedometer signal. Also, this parameter can affect the PTO operation, extended idle and trip totals.
  • Minimum: 0
  • Maximum: 43000 revolutions per km (65000 revolutions per mile).
  • Default: 0

3). Vehicle Speed Cal (J1939-ABS)
The "Vehicle Speed Cal (J1939-ABS)" is used to calculate vehicle speed by using the input from the wheel speed. The data from the wheel speed is transmitted via the J1939 data link. The "Vehicle Speed Input" parameter must be programmed to "Vehicle Speed Cal J1939-ABS". The manufacturer of the ABS must transmit tire revolutions per mile that is based on the tire size. If the tire size is changed from the tire size that is programmed in the ABS the "Vehicle Speed Cal (J1939-ABS)" must be changed. The value that is contained in the "Vehicle Speed Cal (J1939-ABS)" parameter is a ratio. If the actual tire size is equal to the tire size that is programmed in the ABS, the "Vehicle Speed Cal (J1939-ABS)" parameter will be "1". The ratio can be found by dividing the tire revolutions per mile that is transmitted by the ABS by the actual tire revolutions per mile. Contact the manufacturer of the ABS in order to verify that this message is supported.

If the "Vehicle Speed Input" parameter is programmed to "Vehicle Speed Cal J1939-ABS", this parameter must be programmed. If this parameter is not programmed, 253-02 Check Customer or System Parameters will be active. This parameter affects the cruise control and the ECM speedometer signal. Also, this parameter can affect the PTO operation, extended idle and trip totals.
  • Minimum: 0
  • Maximum: 6.550
  • Default: 0

4). Vehicle Speed Limit
The "Vehicle Speed Limit" (VSL) is the maximum vehicle speed that is allowed by the ECM. The ECM will shut off fuel above this speed. An inexperienced driver may think that something is wrong with the engine because the ECM will not fuel the engine above this vehicle speed limit. Vehicle speed limiting allows the implementation of a gear fast/run slow specification for the truck. The gear fast/run slow specification for the truck improves fuel economy while the parameter for the vehicle speed limit limits the maximum vehicle speed of the truck.
  • Minimum: 48 km/h (30 mph)
  • Maximum: 204 km/h (127 mph)
  • Default: 204 km/h (127 mph)

5). VSL Protection
The "VSL Protection" is the maximum engine rpm when there is a problem with the vehicle speed signal that is detected by the ECM. The ECM limits the engine to this engine rpm when the ECM senses no vehicle speed signal, and a load on the engine. This is a feature that is used to prevent tampering by running without a vehicle speed input to the ECM.
Figure 1.3 - VSL Protection (1800 rpm)
Note: When this parameter is programmed to the programmed TEL rpm, the ECM disables 84-01 Vehicle Speed loss of signal and 84-10 Vehicle Speed signal rate of change and the "VSL Protection" may be exceeded by disconnecting the vehicle speed sensor.
  • Minimum: 1000 rpm
  • Maximum: TEL rpm
  • Default: TEL rpm

6). Tachometer Calibration
The "Tachometer Calibration" is used by the ECM to translate the engine speed signal into revolutions per minute for a tachometer. The "Tachometer Calibration" is programmed in pulses per revolution (PPR). The programmable range is from 12.0 PPR to 500.0 PPR in 0.1 PPR increments.
  • Minimum: 12.0 PPR
  • Maximum: 500.0 PPR
  • Default: 113.0 PPR

7). Soft Vehicle Speed Limit
The "Soft Vehicle Speed Limit" operates in conjunction with the "Vehicle Speed Limit". The "Soft Vehicle Speed Limit" limits the vehicle speed within the following range:
-The minimum value is 4 km/h (2.5 mph) below the programmed "Vehicle Speed Limit" at full load.
-The maximum value is 4 km/h (2.5 mph) above the selected "Vehicle Speed Limit" at no load.
  • Alternative: Yes
  • Default: No

8). Two Speed Axle - Low Speed Range Axle Ratio
The "Two Speed Axle - Low Speed Range Axle Ratio" must be programmed when a "Two-Speed Axle On/Off Switch" is used by the ECM to adjust the "Vehicle Speed Calibration". When a two-speed axle is used, the change in gear ratios from the high speed range to the low speed range alters the calibration of the vehicle speed signal. Since the vehicle speed signal has been altered, a calibration adjustment is required to ensure that the ECM driven speedometer and the information that is stored in the ECM correctly reflect the actual vehicle speed. This parameter must be programmed to the actual value of the axle ratio for the low speed range. This parameter only requires programming when the "Two-Speed Axle Switch" parameter is enabled.
  • Minimum: 1.00
  • Maximum: 19.99
  • Default: 1.00

9). Nominal Axle Ration - High Speed Range Axle Ratio
The "Nominal Axle Ration - High Speed Range Axle Ratio" must be programmed when a "Two-Speed Axle On/Off Switch" is used by the ECM to adjust the "Vehicle Speed Calibration". When a two-speed axle is used, the change in gear ratios from the high speed range to the low speed range alters the calibration of the vehicle speed signal. Since the vehicle speed signal has been altered, a calibration adjustment is required to ensure that the ECM driven speedometer and the information that is stored in the ECM correctly reflect the actual vehicle speed. This parameter must be programmed to the actual value of axle ratio for the high speed range. This parameter only requires programming when the "Two-Speed Axle Switch" parameter is enabled.
  • Minimum: 1.00
  • Maximum: 19.99
  • Default: 1.00

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