3500B and 3500B High Displacement Generator Set Engines Caterpillar

The digital sensor supply provides power to all digital sensors. The Electronic Control Module (ECM) supplies 8.0 ± 0.4 VDC from the ECM connector J1/P1 to each digital sensor connector pin "A". The digital sensor return is used as the return line for the digital sensors, for the speed/timing sensors, and for the switch inputs to the ECM. The digital return line is from the ECM connector J1/P1 to each digital sensor connector pin "B". The digital sensor supply is output short circuit protected. A short circuit to the battery will not damage the circuit inside the ECM. The digital sensors are not protected from overvoltage.

The following list contains a description of the digital sensors that are found on the engine.

Left Exhaust Temperature Sensor - The ECM uses the signal from the sensor to monitor left exhaust temperature. The sensor is mounted in the left exhaust manifold before the turbocharger. The sensor output is a constant frequency signal with a pulse width that varies with the exhaust temperature. The output signal is referred to as a duty cycle or as a pulse width modulated signal. The output signal is expressed as a percentage between 0 and 100 percent. The Caterpillar Electronic Technician (ET) will display the exhaust temperature as a value between 49 °C to 850 °C (120 °F to 1562 °F). If the actual temperature is between -40 °C to 49 °C (-40 °F to 120 °F), the display will read 30 °C (86 °F). If the temperature is above 851 °C (1564 °F), the display will read 851 °C (1564 °F).

Right Exhaust Temperature Sensor - The ECM uses the signal from the sensor to monitor right exhaust temperature. The sensor is mounted in the right exhaust manifold before the turbocharger. The sensor output is a constant frequency signal with a pulse width that varies with the exhaust temperature. The output signal is referred to as a duty cycle or as a pulse width modulated signal. The output signal is expressed as a percentage between 0 and 100 percent. The Cat ET will display the exhaust temperature as a value between 49 °C to 850 °C (120 °F to 1562 °F). If the actual temperature is between -40 °C to 49 °C (-40 °F to 120 °F), the display will read 30 °C (86 °F). If the temperature is above 851 °C (1564 °F), the display will read 851 °C (1564 °F).

Note: The engine monitoring system may be programmed by dealers and/or customers. Dealers and/or customers can monitor customized warnings, derates, shutdown override setpoints, and delay times using Cat ET. Customized parameters may affect the behavior of the ECM. The behavior of the ECM may vary from the description that is given in this system operation section. You may refer to the diagnostic procedure Troubleshooting, "Engine Monitoring System" in order to determine if there are any parameters that are affecting engine operation.

Illustration 1	g01020181
Typical example

Test Step 1. Check for Connector Damage.

1. Turn the breaker for the battery to the OFF position.

2. Turn the ECS to the OFF/RESET position.

3. 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.

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

5. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

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

7. 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 are 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 are not okay.

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

  Stop.

Test Step 2. Check for a Short Circuit in the Wiring Harness.

1. Disconnect ECM connector J1/P1 and all of the digital sensors.

2. Measure the resistance between the digital supply P1-35 (A700-OR) and the digital return P1-29 (998-BR) on connector P1.

3. Measure the resistance between the digital supply P1-35 (A700-OR) and engine ground.

4. Measure the resistance between the digital return P1-29 (998-BR) and engine ground.

Expected Result:

The resistance is greater than 20,000 Ohms for each measurement.

Results:

• OK - The resistance is greater than 20,000 Ohms. Proceed to Test Step 3.

• Not OK - The resistance is less than 20,000 Ohms.

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

  Stop.

Test Step 3. Check the Digital Supply Voltage at the ECM.

1. Remove the wire A700-OR from ECM connector P1-35. Install a wire jumper into the socket for wire A700-OR.

2. Remove the wire 998-BR from ECM connector P1-29. Install a wire jumper into the socket for wire 998-BR.

   Note: If you remove the sensor common from the ECM an open circuit diagnostic code will be generated for all sensors that use the sensor common. Troubleshoot the original code. Delete the logged diagnostic codes when you are finished.

3. Turn the breaker for the battery to the ON position.

4. Turn the ECS to the STOP position on engines with the "EMCP II" panel. Turn the ECS to the SERVICE position on engines with the "EMS II" panel.

5. Measure the voltage between the wire jumper in P1-35 and the wire jumper in P1-29.

6. Turn the ECS to the OFF/RESET position.

7. Remove the wire jumpers and reconnect all wires. Reconnect ECM connector J1/P1.

Expected Result:

The supply voltage is 8.0 ± 0.4 VDC.

Results:

• OK - The supply voltage is 8.0 ± 0.4 VDC. The digital sensor supply is producing the correct voltage. Proceed to Test Step 4.

• Not OK - The supply voltage is not 8.0 ± 0.4 VDC. The digital sensor is not producing the correct voltage.

  Repair: Perform the diagnostic functional test Troubleshooting, "Electrical Power Supply".

  Stop.

Test Step 4. Check the Digital Sensor Supply Voltage at the Sensor Connector.

1. Turn the ECS to the STOP position on engines with the "EMCP II" panel. Turn the ECS to the SERVICE position on engines with the "EMS II" panel.

2. Measure the digital sensor supply voltage between the digital supply terminal-A (A700-OR) and the digital return terminal-B (998-BR) of all the digital sensors.

   Note: If the sensor is disconnected from the harness, an open circuit diagnostic code will be generated for that sensor. Troubleshoot the original code. Delete the logged diagnostic codes when you are finished.

3. Turn the ECS to the OFF/RESET position.

Expected Result:

The supply voltage is 8.0 ± 0.4 VDC.

Results:

• OK - The supply voltage is 8.0 ± 0.4 VDC at all of the digital sensor connectors. Proceed to Test Step 5.

• Not OK - The supply voltage is not 8.0 ± 0.4 VDC. There is an open circuit in the harness or connectors.

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

  Stop.

Test Step 5. Check the Digital Sensors for Short Circuits.

1. Disconnect all of the digital sensors.

2. Turn the ECS to the STOP position on engines with the "EMCP II" panel. Turn the ECS to the SERVICE position on engines with the "EMS II" panel.

   Note: If the sensor is disconnected from the harness, an open circuit diagnostic code will be generated for that sensor. Troubleshoot the original code. Delete the logged diagnostic codes when you are finished.

3. Connect one digital sensor at a time.

4. Measure the digital sensor supply voltage between the digital supply terminal-A (A700-OR) and the digital return terminal-B (998-BR) at a different sensor connector. Repeat these steps with all of the digital sensors.

5. Turn the ECS to the OFF/RESET position.

Expected Result:

The supply voltage is 8.0 ± 0.4 VDC.

Results:

• OK - The supply voltage is 8.0 ± 0.4 VDC. The digital sensor supply is correct. The harness and sensors are okay.

  Repair: The problem may be intermittent. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  Stop.

• Not OK - The supply voltage is not 8.0 ± 0.4 VDC when a sensor is reconnected. The sensor may be internally shorted.

  Repair: Temporarily install a new sensor. Ensure that the problem is no longer present. Reinstall the old sensor. If the problem returns, replace the sensor.

  Stop.