HOOD G. 3B0438 - Caterpillar

Software Function
This section gives a brief overview of some of the fault and normal operating conditions where the DMMP will take control of (or limit) the throttle position. All the faults listed will also trigger a fault indication that will be retrievable through the PC Service tool, a generic J1587 service tool, or via flash code on the fault indicator lamp. See the Hardware Troubleshooting section.Actuator to Minimum
The application software will try to force the actuator to minimum in certain critical fault modes:* blocked actuator fault* actuator position fault* actuator fault* engine overspeed* no MPU input signalRefer to the Appendix for definitions and causes for these fault conditions. The actuator position fault and the actuator fault will cause the actuator to go "limp," so it will return to minimum position by the return spring.Idle Governor Control Only
The control will force engine speed to idle and disable the foot pedal input in the following conditions:* idle validation fault* sensor supply fault* foot pedal fault* idle validation contact switch open, if enabled* vehicle door openThe foot pedal will also be disabled when PTO (fast idle) speed control is enabled.A power-down reset is necessary to clear the active faults.Start Fuel Limiter
When engine speed is above 75 rpm, the start fuel limit causes the governor actuator to ramp open until the engine starts. The foot pedal is disabled until the engine starts. Once the engine starts, the foot pedal is enabled and the start fuel limiter ramped out of control.Engine Dynamics Troubleshooting
Idle Speed Dynamics
The idle speed dynamics have been preset at the factory and should provide acceptable performance. Unstable engine operation may be caused by several other outside problems that may appear to be governor control problems, the most probable being governor actuator linkage setup, fuel delivery problems, or ignition problems.With the engine not running, verify that the actuator linkage moves freely through its range and that the throttle body is not sticking in its bore.A way to check for non-governor problems is to increase the Minimum Actuator in the ACTUATOR MONITOR service header (in Manual Calibration mode) until the engine speed is running above the Minimum Speed Reference. This fixes the actuator position and removes the speed control loop effects. Be sure to record the original settings so that they may be restored once testing is done.
To prevent possible death, serious injury, or property damage from an engine overspeed, be prepared to shut down the engine manually while testing the DMMP dynamic response with the actuator set above the minimum stop.
The actuator should hold position without any movement and the engine should be stable. If the speed is drifting or oscillating excessively, try to find a source other than the governor. If the speed is stable, manually move the actuator linkage. The DMMP control should oppose any such movement and try to hold its position. If the actuator feels "weak" or unstable, refer to the ProAct Actuator section.If the testing still points to governor a problem, you may need to