NIPPLE-PIPE 5312434 - Caterpillar

SPN 1611 - Vehicle Motion, SPN 1614 - Vehicle Speed
The Machine ECM is programmed to determine when an Uncommanded Movement Detected (UCMD) event occurs. When the machine speed is greater than 1.0 km/h (0.6 mph), this logic will stop machine movement under the following conditions:
The actual ground speed is higher than the commanded speed for a duration of time. The default speed differential is set at 20 percent. The default time is set at 250 ms.
The actual machine direction is opposite the commanded direction for a specified amount of time.If the Machine ECM detects UCMD, the system generates a Level 3 fault. An active UCMD will disable all propel, and vibe system functions. Propel command will go to zero and the parking brake and two-speed solenoids will be de-energized, causing the parking brake to be applied.
Illustration 1 g03834407
Schematic for the Speed Sensors
The Machine ECM monitors input speed signals from the Drum and Axle speed sensors in order to determine the actual machine speed and direction. Contact 1 of each speed sensor receives 8 volt power. Each speed sensor provides two pulsed input signals to Machine ECM from contacts 3 and 4.The Machine ECM compares the frequency of the two signals from the Drum Speed Sensor. The ECM also compares the frequency of the two input signals from the Axle Speed Sensor. If internal signals from either sensor are out of sync, the Machine ECM generates a Level 2 fault. In this case, the ECM sets the propel mode to low, and the UCMD detection logic and the vibratory system are disabled.The ECM averages the input from the two sensors to calculate the machine speed. The Machine ECM compares the observed machine speed to the desired machine speed. Inputs used to measure the difference between the actual travel speed and travel speed commanded by the operator are:
Motor Speed
Engine Speed
Propel speed range (Hi/Low)
Propel speed control
Propel lever positionThe key switch must be cycled before the Diagnostic Code will be cleared and the machine will be allowed to operate.Causes of an Uncommanded Movement Detected (UCMD) Event
The Pump Stuck at Maximum Displacement - The motor will be running at maximum speed and higher than commanded by the operator. The machine will not be able to slow down to a stop.
Motor Stuck at Minimum Displacement - The actual speed of the motor will be too high compared to the commanded speed by the operator. The (axle/drum) drive loop pressures will be excessive in one loop compared to the other (axle/drum) drive loop pressure.
Detected Travel Direction Opposite – The signal from one or both speed sensors is abnormal or unexpected.
Propel Pump Neutral Adjustment – The machine could move while the propel command is in neutral position and the brake is off. The axle or drum drive loop pressure is greater than charge pressure.
Propel Pump Calibration Incorrect – The actual speed of a propel motor is too high compared to the stored calibration parameters.
Rolling Down Steep Grades - The motor speed will be higher than expected.
Machine Configuration