3126B and 3126E On-highway Engines Caterpillar

"Vehicle Speed Calibration"

This calibration is used when the ECM is configured to use a vehicle speed sensor that is connected to the ECM vehicle harness connector J1/P1:32 & 33.

The "Vehicle Speed Calibration" is the value that is used by the ECM in order to translate the vehicle speed signal into kilometers per hour (miles per hour). When a vehicle speed sensor is connected to an ECM input, the "Vehicle Speed Input" must be programmed to "J1/P1:32 & 33". This parameter is programmed in pulses per kilometer (PPKM) or pulses per mile (PPM). This parameter must be programmed. If this parameter is not programmed, 253-02 Check Customer or System Parameters (56) will become 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.

"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 "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 (56) will become 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.

"Vehicle Speed Cal (J1939 ABS)"

OCT01 and newer Personality Modules.

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 system must transmit tire revolutions per mile that is based on the tire size. If the tire size is changed from tire size that is programmed in the ABS system, 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 system, 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 system by the actual tire revolutions per mile. Contact the manufacturer of the ABS system 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 (56) will become 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.

"Vehicle Speed Limit (VSL)"

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.

"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.

Note: When this parameter is programmed to the TEL rpm, the ECM disables 84-01 Loss Of Vehicle Speed Signal (31) and 84-10 Vehicle Speed Rate of Change (36) and the "VSL Protection" may be exceeded by disconnecting the vehicle speed sensor.

"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 2.0 to 500.0 in increments of 0.1 PPR.

"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.

"Low Speed Range Axle Ratio"

MAR98 and newer Personality Modules.

The "Low Speed Range Axle Ratio" parameter must be programmed when an on/off switch for the two-speed axle 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 should be programmed to the "Low Speed Range Axle Ratio". This parameter only requires programming when the "Two-Speed Axle Switch" parameter is enabled.

"High Speed Range Axle Ratio"

This parameter only requires programming when the "Two-Speed Axle Switch" parameter is enabled. The "High Speed Range Axle Ratio" must be programmed when an on/off switch for the two-speed axle 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 should be programmed to the "High Speed Range Axle Ratio".