3500B Marine Engines Caterpillar


Throttle Position Sensor

Usage:

3508B 1TW
System Operation Description:

Note: This test is for the Port throttle position sensor. If you are troubleshooting the Starboard throttle position sensor, refer to the schematic for proper wire numbers.

The throttle position sensor is used to provide a throttle signal to the Electronic Control Module (ECM). The sensor output is a constant frequency signal with a pulse width that varies with the throttle position. This output signal is referred to as the Pulse Width Modulated signal (PWM). This signal is expressed as a percentage between 0 percent and 100 percent.

The sensor will produce a duty cycle of 5 percent to 10 percent at low idle and 90 percent to 95 percent at high idle. The percent duty cycle is translated in the ECM into the throttle position of 0 percent to 100 percent. The sensor is powered by a switched battery connection to pin-A. Use this procedure to troubleshoot an active diagnostic code of 91-08 Throttle Position signal abnormal. The ECM will not respond to the throttle position sensor if there is an active 253-02 Personality Module mismatch.

The desired engine speed should change when the throttles are moved. If the desired engine speed does not change, continue performing this test. If the desired engine speed changes, proceed to Troubleshooting, "Synchronization Switch Not Functioning Properly".



Illustration 1g00983926


Illustration 2g00725481
Throttle Position Versus PWM Input


Illustration 3g00725482
Stops for the throttle position sensor

Test Step 1. Check for Connector Damage.

  1. Disconnect the main power.

  2. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.

  3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.

  4. Check the ECM connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

  5. Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

  6. Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring should be free of corrosion, of abrasion or of pinch points.

Results:

  • OK - The connectors and wiring are okay. Proceed to Test Step 2.

  • Not OK - The connectors and/or wiring need repair.

    Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

    STOP

Test Step 2. Check the Throttle Position Sensor Supply Voltage at the Sensor.

  1. Turn the ECS to the STOP position. The engine should be OFF.

  2. Disconnect the throttle position sensor.

  3. Measure the voltage at J35-A with reference to J35-B.

Expected Result:

The voltage should be approximately 24 ± 3 VDC.

Results:

  • OK - The voltage is approximately 24 ± 3 VDC. The throttle position sensor is receiving the correct voltage. Proceed to Test Step 3.

  • Not OK - The voltage is not 24 ± 3 VDC. The sensor is not receiving the correct voltage. Proceed to Test Step 6.

Test Step 3. Check the Throttle Position Sensor Duty Cycle at the Sensor Connector.



Illustration 4g00725507

  1. Remove the signal wire for the throttle position sensor from connector J35/P35.

  2. Remove pin C from the connector P35. Place the red probe of the multimeter on pin C. Place the black probe of the multimeter on the − Battery terminal.

  3. Set the multimeter to "VDC".

  4. Press the "HZ" button twice so the % symbol is displayed.

  5. Measure the percent duty cycle of the throttle position sensor. Move the throttle from LOW idle position to HIGH idle position.

Expected Result:

The duty cycle should be 5 to 10 percent at the low idle position. The duty cycle should be 90 to 95 percent when the handle is fully activated.

Results:

  • OK - The duty cycle is 5 to 10 percent at the low idle position. The duty cycle is 90 to 95 percent when the handle is fully activated. Proceed to Test Step 4.

  • Not OK - The duty cycle is 0 percent or the duty cycle does not change smoothly.

    Repair: Replace the throttle position sensor. Perform the diagnostic functional test Troubleshooting, "Throttle Position Sensor - Calibrate" after you replace the sensor.

    STOP

  • Not OK - The duty cycle is changing but the duty cycle does not reach the low idle and/or the high idle positions.

    Repair: Recalibrate the sensor so that the duty cycle is 5 to 10 percent at the low idle stop and the duty cycle is 90 to 95 percent at the high idle stop. Refer to the diagnostic functional test Troubleshooting, "Throttle Position Sensor - Calibrate".

    STOP

Test Step 4. Check the Throttle Position Sensor Duty Cycle at the J3 Customer Connector.

  1. Reinsert pin C into the connector for the throttle position sensor P35.

  2. Remove pin J3-03 from the customer connector J3 for the port engine.

  3. Use a multimeter and place the red probe on J3-03. Place the black probe on the − Battery terminal.

  4. Measure the percent duty cycle of the throttle position sensor. Move the throttle from LOW idle position to HIGH idle position.

Expected Result:

The duty cycle should be 5 to 10 percent at the low idle position. The duty cycle should be 90 to 95 percent at the high idle stop.

Results:

  • OK - The duty cycle is 5 to 10 percent at the low idle position. The duty cycle is 90 to 95 percent at the high idle stop. Proceed to Test Step 5.

  • Not OK - The duty cycle is 0 percent or the duty cycle does not change smoothly.

    Repair: Replace the wire from P35-C to J3-03.

    STOP

Test Step 5. Check the Throttle Position Sensor Duty Cycle at the ECM Connector.

  1. Turn the ECS to the OFF position.

  2. Remove the ECM connector P2 from the primary ECM. Remove the signal wire P2-24 for the throttle position sensor from the ECM connector P2.

  3. Reconnect the ECM connector J2/P2.

  4. Place the red probe on the wire that was removed from P2-24 of the ECM connector P2. Place the black probe on the − Battery terminal.

  5. Measure the percent duty cycle of the throttle position sensor. Move the throttle from LOW idle position to HIGH idle position.

  6. Replace all connectors and wires.

Expected Result:

The duty cycle should be 5 to 10 percent at the low idle stop. The duty cycle should be 90 to 95 percent at the high idle stop.

Results:

  • OK - The Duty Cycle and Throttle Position readings are correct.

    Repair: Temporarily replace the ECM and perform the test again. If the problem is resolved, the ECM is faulty. Permanently replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".

    STOP

  • Not OK - The duty cycle reading is not correct. The throttle position signal is not reaching the ECM.

    Repair: Replace the wire from J3-03 to J2-24. Verify that the repair eliminates the problem.

    STOP

Test Step 6. Check the Voltage from the "EMS relay" to the Throttle Position Sensor.

  1. Turn the ECS to the STOP position.

  2. Measure the voltage between terminal 30 on the "EMS relay" and the − Battery terminal.

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

  • OK - The voltage measures 24 ± 3 VDC.

    Repair: Repair the connectors or wiring and/or replace the connectors or wiring between the "EMS relay" and the throttle position sensor. Check for voltage at TB-18 and the connector for the instrument box. Refer to Illustration 1 as a reference.

    STOP

  • Not OK - The voltage does not measure 24 ± 3 VDC. Proceed to Test Step 7.

Test Step 7. Check the Voltage at the Coil of the "EMS relay".

  1. Turn the ECS to the STOP position.

  2. Measure the voltage between terminal 86 on the "EMS relay" and the − Battery terminal.

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

  • OK - The voltage measures 24 ± 3 VDC.

    Repair: Verify that 24 ± 3 VDC is present on terminal 87 of the "EMS relay". If voltage is not present on terminal 87 of the "EMS relay", check the wiring and check the breakers between the "EMS relay" and the battery.

    If voltage is present on terminal 87 of the "EMS relay", verify that wire 200-BK(Black) has continuity to the − Battery terminal. If wire 200-BK(Black) is okay, replace the "EMS relay".

    STOP

  • Not OK - The voltage does not measure 24 ± 3 VDC. Proceed to Test Step 8.

Test Step 8. Check the Voltage at the Emergency Stop Switch.

  1. Turn the ECS to the STOP position.

  2. Measure the voltage between terminal 4 on the emergency stop switch and the − Battery terminal.

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

  • OK - The voltage measures 24 ± 3 VDC.

    Repair: Verify that 24 ± 3 VDC is present on terminal 3 of the emergency stop switch. If voltage is not present on terminal 3 of the emergency stop switch, replace the emergency stop switch.

    If voltage is present on terminal 3 of the emergency stop switch, repair the wire 114-RD(Red) between terminal 3 of the emergency stop switch and terminal 86 of the "EMS relay".

    STOP

  • Not OK - The voltage does not measure 24 ± 3 VDC.

    Repair: If voltage is not present on terminal 4 of the emergency stop switch, verify that voltage is present on terminal 16 of the ECS. If voltage is present on terminal 16 of the ECS, repair the wire 113-OR(Orange) between the ECS and the emergency stop switch.

    If voltage is not present on terminal 16 of the ECS, verify that voltage is present on terminal 1 of the ECS. If voltage is present on terminal 1 of the ECS, perform the diagnostic functional test Troubleshooting, "Engine Control Switch".

    If voltage is not present on terminal 1 of the ECS, check the wiring and check the breakers between the ECS and the battery. Refer to Illustration 1 as a reference.

    STOP

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