GUIDE AS 9R9152 - Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the circuit that is for the throttle position sensor or if one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
Code and Description Conditions which Generate this Code System Response
91-8 Throttle Position Sensor abnormal frequency, pulse width, or period The Electronic Control Module (ECM) detects a signal frequency for the primary throttle position sensor that is below 150 Hz or the frequency is above 1050 Hz. The engine must be running in order for this code to be logged.
The ECM flags the throttle position as invalid data and a default value of zero percent is used. The engine speed is limited to low idle.
91-13 Throttle Position Sensor calibration required The ECM detects a duty cycle for the primary throttle position sensor that is below 5 percent or a duty cycle is above 95 percent.
1249-8 Secondary Throttle Position signal abnormal The ECM detects a signal frequency for the secondary throttle position sensor that is below 150 Hz or the frequency is above 1050 Hz.
1249-13 Secondary Throttle Position Sensor calibration required The ECM detects a duty cycle for the secondary throttle position sensor that is below 5 percent or a duty cycle is above 95 percent. Note: If the vessel is equipped with a Multi-Station Control System (MSCS), refer to Service Manual, RENR7651, "Marine Multi-Station Control System" for additional information that is related to troubleshooting the speed control circuits.Note: When you make repairs to the circuit for the Throttle Position Sensor (TPS), follow the guidelines that are found in Special Instruction, REHS1187, "Electronic Installation Guide". This document provides information that ensures that the TPS is protected from transient voltages and from problems that are caused by improper grounding.Note: If one of the above diagnostic codes is active, troubleshoot that code before you continue with this procedure. If you suspect a problem with engine synchronization, refer to Troubleshooting, "Synchronization - Test".A problem with the circuit for the synchronization switch may prevent the ECM from responding to a valid signal from the TPS. The following active diagnostic codes will also prevent the ECM from responding to the throttle input:
91-13 Throttle Position Sensor calibration required
1249-13 Secondary Throttle Position Sensor calibration requiredIf one of the above diagnostic codes is active, troubleshoot that code before you continue with this procedure. If you suspect a problem with engine synchronization, refer to Troubleshooting, "Synchronization - Test".The TPS provides the throttle signal to the engine's ECM. The output for rated speed is a Pulse Width Modulated Signal (PWM) at a constant frequency. The TPS produces a minimum duty cycle in the lowest position and a maximum duty cycle in the highest position of the sensor. When the sensor is in the lowest position, the ECM translates the sensor's output signal to a throttle position of 0 percent. When the sensor is placed in the highest position, the ECM translates the output signal to a throttle position of 100