Speed Control (PWM) - Test
Use this procedure to troubleshoot the electrical system if a problem is suspected with the throttle input.
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| 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 Engine Electronic Control Module (ECM) detects a sensor frequency that is less than 150 Hz or a sensor frequency that is greater than 1000 Hz for 2 seconds. | The diagnostic code is active and the code is logged. The throttle signal defaults to a zero percent duty cycle. |
| 91-10 Throttle Position Sensor : Abnormal Rate of Change | The Engine Electronic Control Module (ECM) detects a sensor frequency that is changing at an abnormal rate. | The diagnostic code is active and the code is logged. |
| 91-13 Throttle Position calibration required | The duty cycle for the throttle position sensor signal is less than 5 percent or more than 95 percent. | The diagnostic code is active and the code is logged. |
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| Illustration 1 | g03845662 |
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| Troubleshooting Test Steps | Value | Results |
|---|---|---|
1. Inspect the Electrical Connectors and the Wiring Harness. A. Remove electrical power from the ECM. B. Thoroughly inspect the J1/P1 ECM connector. Inspect the J17/P17 customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. C. Perform a D. Check the allen head screw on the ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values. |
Electrical connectors and wiring |
Result : The electrical connectors and wiring are OK. Proceed to Test Step 2. Result : The electrical connectors and wiring are NOT OK. Repair : Repair the wiring and connectors or replace the wiring or the connectors. Ensure that all of the seals are properly connected. Verify that the repair eliminates the problem. If the problem is not resolved, proceed to Test Step 2. |
2. Check Throttle and Droop Readings on Cat® Electronic Technician (ET). A. Connect to the service tool connector. Note : Disconnect the wires from the output terminals when you troubleshoot a generator with a load share module. Connect a 9X-9591 Electrical Converter Gp with a 122-9458 Potentiometer to the wires. Do not attempt to parallel the generator when the load share module is disconnected. B. Turn the engine control switch to the ON position. C. Record the throttle position and the readings of the droop on Cat ET. D. Record the throttle position reading and the reading of the droop on Cat ET during the movement of the throttle setting and the droop setting from minimum to maximum. E. Turn the engine control switch to the OFF position. |
Throttle and Droop status |
Result : The throttle and droop status are OK. Repair : The throttle Input is working properly. Reset the throttle and the droop to the original settings. Reconnect all wires. Result : The throttle and droop status are NOT OK. Proceed to Test Step 3. |
3. Check the Supply Voltage for the Throttle Module. A. Turn the engine control switch to the ON position. B. Measure the voltage between terminal (+B) and terminal (-B) of the throttle module. C. Turn the engine control switch to the OFF position. |
Supply voltage between 24 VDC and 27 VDC |
Result : The supply voltage is OK. Proceed to Test Step 4. Result : The supply voltage is NOT OK. Repair : The throttle module is not receiving the correct voltage. Repair the wiring or replace the wiring. If the problem is not resolved, proceed to Test Step 4. |
4. Check the Isolated Throttle Signal at the Throttle Module. A. Turn the engine control switch to the OFF position. B. Remove the wire from terminal (S) of the throttle module. C. Turn the engine control switch to the ON position. D. Measure the duty cycle between terminal (S) and terminal (-B). Record the duty cycle during the movement of the throttle input from low idle to high idle. E. Measure the frequency between terminal (S) and terminal (-B). Record the frequency during the movement of the throttle input from low idle to high idle. F. Reconnect the wire to terminal (S). G. Turn the engine control switch to the OFF position. The measurement of the duty cycle is between 5 percent and 10 percent while the throttle input is set to the low idle position. The measurement of the duty cycle is between 90 percent and 95 percent while the throttle input is set to the high idle position. The frequency is between 400 Hz and 600 Hz. |
Throttle signal |
Result : The throttle signal is OK. Proceed to Test Step 5. Result : The throttle signal is NOT OK. Repair : Replace the throttle module. If the problem is not resolved, proceed to Test Step 5. |
5. Check the Isolated Droop Signal of the Duty Cycle at the Throttle Module. A. Turn the engine control switch to the OFF position. B. Remove the wire from terminal (D) of the throttle module. C. Turn the engine control switch to the ON position. D. Measure the duty cycle between terminal (D) and terminal (-B). Record the measurement of the duty cycle during the movement of the input for the droop from the low position to the high position. E. Measure the frequency between terminal (D) and terminal (-B). Record the frequency during the movement of the input for the droop from the low position to the high position. F. Turn the engine control switch to the OFF position. G. Reconnect the wire to terminal (D). The duty cycle is between 5 percent and 10 percent while the throttle input is set to the LOW IDLE position. The duty cycle is between 90 percent and 95 percent while the throttle input is set to the HIGH IDLE position. The frequency is between 400 Hz and 600 Hz. |
Droop signal |
Result : The duty cycle is OK. Proceed to Test Step 6. Result : The duty cycle is NOT OK. Repair : Replace the throttle module. If the problem is not resolved, proceed to Test Step 6. |
6. Check the Throttle and the Droop Signal at the ECM. A. Turn the engine control switch to the ON position. B. Measure the duty cycle of the throttle signal between pin 8 of connector P14 and engine ground. Record the duty cycle during the movement of the throttle input from low idle to high idle. C. Measure the duty cycle of the droop signal between pin 37 of ECM connector P14 and engine ground. Record the duty cycle during the movement of the throttle input from low droop to high droop. D. Turn the engine control switch to the OFF position. The duty cycle is between 5 percent and 10 percent while the throttle input is set to the low idle position. The duty cycle is between 90 percent and 95 percent while the throttle input is set to the high idle position. |
Throttle and Droop signal |
Result : The throttle and droop signal are OK. Proceed to Test Step 7. Result : The throttle and droop signal are NOT OK. Repair : The throttle module is producing the correct signal. The signal is not reaching the ECM. Repair the wiring harness or replace the wiring harness. If the problem is not resolved, proceed to Test Step 7. |
7. Check The ECM. A. Connect Cat ET to the service tool connector. B. Turn the engine control switch to the ON position. C. Record the duty cycle of the throttle position sensor from Cat ET during the movement of the throttle input from low idle to high idle. D. Record the droop from Cat ET during the movement of the setting for the droop from minimum to maximum. The duty cycle is between 5 percent and 10 percent while the throttle input is set to the low idle position. The duty cycle is between 90 percent and 95 percent while the throttle input is set to the HIGH IDLE position. |
ECM |
Result : The ECM is OK. The throttle module is operating properly. STOP Result : The ECM is NOT OK. Repair : Disconnect connector P14 and check for damage or corrosion on pin 37 and pin 8. If the problem is not resolved, replace the ECM. Refer to Troubleshooting, "ECM - Replace". |
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