Refer to Systems Operation, "Electronic Control System Components" for diagnostic codes and for diagnostic code information. For an explanation of each diagnostic code, refer to Troubleshooting .
Diagnostic codes are used by the engine system to warn the vehicle operator of a problem. Also, diagnostic codes are used by the engine system to indicate the nature of a problem to the service technician. Some codes are used only to record an event. These codes do not indicate problems that need repair.
An "ACTIVE" diagnostic code represents a problem that should be investigated promptly. The problem should be corrected as soon as possible. Repairing the cause of an "ACTIVE" code will cause the code to be cleared.
When an "ACTIVE" code is generated, the diagnostic lamp will turn on and the diagnostic lamp will remain on. While the diagnostic lamp is turned on, the diagnostic lamp will blink at five second intervals. If the condition that generates the fault occurs for only a brief moment, the lamp will turn off after five seconds. In this situation, the code will be logged.
Logged Diagnostic Codes And Events
When the ECM generates a diagnostic code, the code will be active and the code may be logged in permanent memory within the ECM. The ECM has an internal diagnostic clock and the ECM will record the time for the fault logging. Knowing the time and frequency of the code can be a valuable indication when a technician is troubleshooting intermittent problems. Logged codes can be downloaded or erased with an electronic service tool. These logged codes can also be a valuable indication when a technician is troubleshooting intermittent problems.
Diagnostic Codes that are logged repeatedly may indicate a problem that needs special investigation. Some codes may not need attention until a scheduled maintenance interval. If only both of the following conditions occur, the code may not need any attention until a scheduled maintenance interval:
- the logged code has occurred a few times.
- the code does not result in concerns from the operator.
Certain fault codes and/or event codes cause the system to make major changes in the following parameters:
- engine operation
- limits of engine operation
These changes result from the generation of the code.
Note: The most likely cause of an intermittent problem is a faulty connection or damaged wiring. The next most likely cause of an intermittent problem is a component failure. A sensor or a switch are typical examples of components that could fail. The least likely cause of an intermittent problem is the ECM.
The Caterpillar electronic service tools for the electronic control systems are designed to help the service technician analyze diagnostic codes and problems within the system. Also, the Caterpillar electronic service tools for the electronic control systems are designed to help the service technician locate diagnostic codes and problems within the system. The electronic service tool is required to perform sensor calibrations and the electronic service tool is required in order to monitor programmable parameters of the engine. Also, the electronic service tool is required in order to change programmable parameters of the engine. For a list of service tools and procedures, refer to Troubleshooting .
The Throttle Position Sensor (TPS) is used to provide a throttle signal to the Electronic Control Module (ECM). Sensor output is a constant frequency signal with a pulse width that varies with the throttle position. This output signal is called a "Duty Cycle" or a "Pulse Width Modulation" signal. This output signal is expressed as a percentage between 0 percent and 100 percent.
The sensor will produce a "Duty Cycle" between 10 percent and 22 percent at the low idle throttle position. The sensor will produce a "Duty Cycle" between 75 percent and 90 percent at the maximum throttle position. The ECM converts The "Duty Cycle" signal into a throttle position signal of 3 percent at low idle and 100 percent at maximum throttle.
Note: The remote mounted throttle sensor can get out of calibration. There is a calibration procedure for the sensor. This sensor may be used in a PTO system. If the sensor requires calibration, refer to Special Instruction, SEHS9857, "PTO Installation And Applications Instruction" .
Accelerator Pedal Position Sensor (If Equipped)
The accelerator pedal position sensor is mounted on the back of the accelerator pedal that is supplied by the OEM. No adjustments are required for this sensor. The accelerator pedal position sensor is calibrated automatically by the ECM. The correct calibration can be displayed by the electronic service tool. The correct throttle signal is displayed as 3 percent when the accelerator pedal is not depressed. The correct throttle signal is displayed as 100 percent when the accelerator pedal is completely depressed.