The throttle and the inputs of the droop to the ECM are provided by a throttle or by a load share module. The inputs are provided through the wiring of the equipment. These inputs are constant frequency signals with a variable pulse width. The signals are expressed as a percentage between 0 and 100 percent duty cycle.
The throttle signal and the input signal of the droop have a duty cycle of 5 percent to 10 percent for low throttle and 90 percent to 95 percent at full throttle. The throttle signal is translated by the ECM into the throttle position between 0 and 100 percent. The signal for the droop is translated into a setting for the droop of 0 to 10 percent.
Use this procedure to troubleshoot the electrical system if a problem is suspected with the throttle input or if the diagnostic code in Table 1 is active.
| Diagnostic Codes Table | |||
|---|---|---|---|
| Code and Description | Flash Code | Conditions which Generate this Code | System Response |
| 91-8 Throttle Position Sensor : Abnormal Frequency, Pulse Width, or Period | 32 | The Engine's 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 two 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 | 32 | The Engine's Electronic Control Module (ECM) detects a sensor frequency that is changing at a abnormal rate. | The diagnostic code is active and the code is logged. |
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| Illustration 1 | g01646874 |
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| Illustration 2 | g01646895 |
(08) Primary throttle (37) Droop | |
Test Step 1. Inspect the Electrical Connectors and the Wiring Harness
- Remove electrical power from the ECM.
- Thoroughly inspect the J14/P14 ECM connector. Inspect the J17/P17 customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit.
- Check the allen head screw on the ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.
Results:
- OK - All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points. Proceed to Test Step 2.
- NOT OK - There is a problem with the connectors and/or the wiring.
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.
STOP
Test Step 2. Check Throttle and Droop Readings on Caterpillar Electronic Technician (ET)
- 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.
- Turn the engine control switch to the ON position.
- Record the throttle position and the readings of the droop on Cat ET.
- 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.
- Turn the engine control switch to the OFF position.
Expected Result:
The status of the throttle changes from 0 percent to 100 percent as the throttle input is changed from low idle to high idle.
The status of the droop changes from 0 percent to 10 percent as the input of the droop is changed from low droop to high droop.
Results:
- OK - The status of the throttle changes from 0 percent to 100 percent as the throttle input is changed from low idle to high idle. The status of the droop should change from 0 percent to 10 percent as the input of the droop is changed from low droop to high droop.
Repair: The throttle Input is working properly. Reset the throttle and the droop to the original settings. Reconnect all wires.
STOP
- NOT OK - The status of the throttle does not change from 0 percent to 100 percent as the throttle input is changed from low idle to high idle. The status of the droop does not change from 0 percent to 10 percent as the input of the droop is changed from low droop to high droop. Proceed to Test Step 3.
Test Step 3. Check the Supply Voltage for the Throttle's Module
- Turn the engine control switch to the ON position.
- Measure the voltage between terminal (+B) and terminal (-B) of the throttle's module.
- Turn the engine control switch to the OFF position.
Expected Result:
The voltage measures between 24 VDC and 27 VDC
Results:
- OK - The voltage is between 24 VDC and 27 VDC. Proceed to Test Step 4.
- NOT OK - The voltage is not between 24 VDC and 27 VDC.
Repair: The throttle's module is not receiving the correct voltage. Repair the wiring or replace the wiring.
STOP
Test Step 4. Check the Isolated Throttle Signal at the Throttle's Module
- Turn the engine control switch to the OFF position.
- Remove the wire from terminal (S) of the throttle's module.
- Turn the engine control switch to the ON position.
- 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.
- 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.
- Reconnect the wire to terminal (S) .
- Turn the engine control switch to the OFF position.
Expected Result:
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.
Results:
- OK - 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. Proceed to Test Step 5.
- NOT OK - The measurement of the duty cycle is not between 5 percent and 10 percent while the throttle input is set to the low idle position. The measurement of the duty cycle is not between 90 percent and 95 percent while the throttle input is set to the high idle position. The frequency is not between 400 Hz and 600 Hz.
Repair: Replace the throttle's module.
STOP
Test Step 5. Check the Isolated Droop Signal of the Duty Cycle at the Throttle's Module
- Turn the engine control switch to the OFF position.
- Remove the wire from terminal (D) of the throttle's module.
- Turn the engine control switch to the ON position.
- 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.
- 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.
- Turn the engine control switch to the OFF position.
- Reconnect the wire to terminal (D).
Expected Result:
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.
Results:
- OK - 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. Proceed to Test Step 6.
- NOT OK - The duty cycle is not between 5 percent and 10 percent while the throttle input is set to the LOW IDLE position. The duty cycle is not between 90 percent and 95 percent while the throttle input is set to the HIGH IDLE position. The frequency is not between 400 Hz and 600 Hz.
Repair: Replace the throttle's module.
STOP
Test Step 6. Check the Throttle and the Droop Signal at the ECM
- Turn the engine control switch to the ON position.
- 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.
- 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.
- Turn the engine control switch to the OFF position.
Expected Result:
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.
Results:
- OK - 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. Proceed to Test Step 7.
- NOT OK - The duty cycle is not between 5 percent and 10 percent while the throttle input is set to the LOW IDLE position. The duty cycle is not between 90 percent and 95 percent while the throttle input is set to the HIGH IDLE position.
Repair: The throttle's module is producing the correct signal. The signal is not reaching the ECM. Repair the wiring harness or replace the wiring harness.
STOP
Test Step 7. Check The ECM
- Connect Cat ET to the service tool connector.
- Turn the engine control switch to the ON position.
- 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.
- Record the droop from Cat ET during the movement of the setting for the droop from minimum to maximum.
Expected Result:
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.
Results:
- OK - 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 theHIGH IDLE position.
Repair: The throttle's module is operating properly.
STOP
- NOT OK - The duty cycle is not between 5 percent and 10 percent while the throttle input is set to the LOW IDLE position. The duty cycle is not between 90 percent and 95 percent while the throttle input is set to the HIGH IDLE position.
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".
STOP