SENSOR GP-SPEED 5221643 - Caterpillar

System Operation
Engine Governor
The ECM governs the engine. The ECM determines the timing, the injection pressure, and the amount of fuel that is delivered to each cylinder. These factors are based on the actual conditions and on the desired conditions at any given time during starting and operation.The ECM uses the throttle position sensor to determine the desired engine speed. The ECM compares the desired engine speed to the actual engine speed. The actual engine speed is determined through interpretation of the signals that are received by the ECM from the engine speed/timing sensors. If the desired engine speed is greater than the actual engine speed, the ECM requests that more fuel is injected in order to increase engine speed.Timing Considerations
Once the ECM has determined the amount of fuel that is required, the ECM must determine the timing of the fuel injection. The ECM adjusts timing for optimum engine performance and for the fuel economy. Actual timing and desired timing cannot be viewed with the electronic service tool. The ECM determines the location of top center of the number one cylinder from the signals that are provided by the engine speed/timing sensors. The ECM determines when injection should occur relative to the top center. The ECM then provides the signal to the injector at the desired time.Fuel Injection
The ECM sends a high voltage signal to the injector solenoids in order to energize the solenoids. By controlling the timing and the duration of the high voltage signal, the ECM can control the following aspects of injection:
Injection timing
Fuel deliveryOther ECM Functions for Performance
Refer to Troubleshooting, "Configuration Parameters" for supplemental information about the systems that can be monitored by the ECM.Programmable Parameters
Certain parameters that affect engine operation may be changed with the electronic service tool. The parameters are stored in the ECM. These parameters are either system configuration parameters or customer parameters.System configuration parameters are set at the factory. System configuration parameters affect emissions or power ratings within an engine family.Some of the parameters may affect engine operation in an unusual way. An operator might not expect this type of effect. Without adequate training, these parameters may lead to power complaints or performance complaints even though the engines performance is to the specification.Customer parameters are variable. Customer parameters can be used to affect the characteristics of the engine. Limits are set by the factory and by the monitoring system.Refer to Troubleshooting, "Configuration Parameters" for additional information on this subject.