3512 and 3516 EUI Engines for 784B, 785B, 789B and 793B Off-Highway Trucks Caterpillar

The Electronic Control Module (ECM) provides the engine speed/timing sensor with 13 ± 0.5 VDC. The engine speed/timing sensor provides a pulse signal to the ECM. The signal is created as the timing reference gear rotates past the pickup of the engine speed/timing sensor. The timing reference gear is mounted on the rear of the left camshaft. A unique tooth pattern on the timing reference gear allows the ECM to determine the crankshaft position, engine rotation, and engine rpm.

The engine speed/timing sensor generates a pulse signal to the ECM as each tooth passes the sensor. The ECM counts the pulses in order to determine the engine rpm. The ECM memorizes the pattern of the pulses. The ECM compares that pattern to a standard pattern in order to determine the crankshaft position. The ECM uses this information to determine the No. 1 cylinder. The ECM then triggers each unit injector to fire in the correct firing order and at the correct time. The actual timing and duration of each injection is determined by the ECM. The ECM uses engine rpm and engine load to determine the timing and duration of injection. The loss of the timing signal from the engine speed/timing sensor generates an alert on the status screen of the Caterpillar Electronic Technician (ET). The loss of the timing signal from the engine speed/timing sensor triggers the termination of the signals to the fuel injectors by the ECM.

The throttle position sensor receives 13 ± 0.5 VDC from ECM connector P1-37 to pin A at the sensor connector. The sensor return line is pin B of the sensor connector. Pin B is connected to the digital return line P1-9 of the ECM. The sensor signal is pin C of the sensor connector. Pin C is connected to P1-24 of the ECM.

Note: When the timing gear is installed backward, the ECM generates a diagnostic code of CID-FMI 190-08. If this code is active the ECM will not fire the injectors.

Illustration 1	g00935356

Test Step 1. Check for Connector Damage.

1. Turn the keyswitch to the OFF position.

2. Thoroughly inspect the ECM connector J1/P1 and the machine connector 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 machine 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:

The connectors and wiring are free of the following problems: damage, corrosion, abrasion and incorrect attachment.

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

  Stop.

Test Step 2. Check for an "ACTIVE" Diagnostic Code.

1. Connect Cat ET to the cab service tool connector J31. Start Cat ET.

2. Turn the keyswitch to the ON position. The engine should be off.

3. Access the logged diagnostic codes on Cat ET.

Expected Result:

The Cat ET screen indicates a CID-FMI 190-02 or a CID-FMI 190-08.

Results:

• OK - The CID-FMI 190-02 or a CID-FMI 190-08 is present. Proceed to Test Step 3.

Test Step 3. Check the Engine Speed/Timing Sensor.

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NOTICE
Be sure to extend the sliphead before you install the Engine Speed/Timing Sensor. Also check that the Timing Gear is in a position that will not allow the sliphead of the Engine Speed/Timing Sensor to protrude into one of the slots of the Timing Gear. This is done visually with a flashlight prior to the installation of the Engine Speed/Timing Sensor. Turn the crankshaft to rotate the Timing Gear, if necessary, to position the gear in a place that will not allow the sliphead to protrude into a slot. If the sensor sliphead does protrude into one of the slots, the sliphead wll be broken off as the gear begins to rotate.

1. Turn the keyswitch to the OFF position.

2. Disconnect connector J19/P19 and remove the engine speed/timing sensor.

3. Inspect the plastic sliphead for damage.

4. Check the tension. Gently extend the sliphead 3.5 mm (0.14 inch). Return the sliphead to the original position.

5. Extend the sliphead.

6. Install the engine speed/timing sensor.

Expected Result:

The sliphead requires at least 22 N (5 lb) of force in order to push in the sliphead from the extended position.

Results:

• OK - The sensor and the sliphead are undamaged. The tension on the sliphead is normal. Reinstall the sensor. Proceed to Test Step 4.

• Not OK - The engine speed/timing sensor or the sliphead is damaged and/or the sliphead has insufficient tension.

  Repair: Replace the engine speed/timing sensor. Calibrate the sensor. Perform the calibration procedure Troubleshooting, "Engine Speed/Timing Sensor - Calibrate".

  Stop.

Test Step 4. Check the Engine RPM on the Cat ET.

1. Connect Cat ET to the cab service tool connector J31. Start the Cat ET.

2. Turn the keyswitch to the ON position. Start the engine, when possible.

3. Crank the engine. Observe the engine speed on Cat ET.

Expected Result:

Cat ET displays a steady engine speed between 100 and 250 rpm while the engine is cranking.

Results:

• OK - The Cat ET screen displays a steady engine speed between 100 and 250 rpm while the engine is cranking. The engine speed/timing sensor is operating normally at this time.

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

  Stop.

• Not OK - The Cat ET screen does not display a steady engine speed between 100 and 250 rpm while the engine is cranking. The Cat ET screen does not display the correct engine rpm signal. Proceed to Test Step 5.

Test Step 5. Check the Supply Voltage to the Sensor.

1. Disconnect the engine speed/timing connector J19/P19.

2. Turn the keyswitch to the ON position. The engine should be off.

3. Measure the voltage at the connector for the engine speed/timing sensor between J19-A and J19-B.

Expected Result:

The supply voltage is 13 ± 0.5 VDC.

Results:

• OK - The supply voltage is 13 ± 0.5 VDC. The sensor is receiving the correct supply voltage. Proceed to Test Step 6.

• Not OK - The supply voltage is not 13 ± 0.5 VDC. The supply voltage is incorrect. Proceed to Test Step 8.

Test Step 6. Check the Signal Voltage at the Sensor.

1. Reconnect all connectors.

2. Remove the signal wire from the sensor connector P19-C.

3. Reconnect connector J19/P19.

4. Measure the voltage between the signal wire and engine ground. Crank the engine and measure the voltage between the signal wire and engine ground.

5. Turn the keyswitch to the OFF position.

6. Reinsert the sensor signal wire back into P19-C.

Expected Result:

The voltage should measure less than 3 VDC or more than 9 VDC when the keyswitch is in the ON position and the engine is not cranking. While the engine is cranking, the voltage is between 2.0 VDC and 7.0 VDC.

Note: The voltage output is determined by the presence or the absence of a tooth on the timing gear.

Results:

• OK - The engine speed/timing sensor is producing the correct output signal. Proceed to Test Step 7.

• Not OK - The engine speed/timing sensor is not producing the correct output signal.

  Repair: Replace the engine speed/timing sensor. Calibrate the sensor. Perform the calibration procedure Troubleshooting, "Engine Speed/Timing Sensor - Calibrate".

  Stop.

Test Step 7. Check the Signal Voltage at the ECM.

1. Turn the keyswitch to the OFF position.

2. Remove the signal wire 999-WH from ECM connector P1-24.

3. Turn the keyswitch to the ON position. The engine should be off.

4. Measure the voltage between the signal wire 999-WH from ECM connector P1-24 and the engine ground.

5. Crank the engine. Measure the voltage between wire 999-WH and the engine ground.

6. Turn the keyswitch to the OFF position.

7. Reconnect all wires and connectors.

Expected Result:

The voltage measures less than 3 VDC or more than 9 VDC when the keyswitch is in the ON position and the engine is not cranking. While the engine is cranking, the voltage is between 2.0 VDC and 7.0 VDC.

Note: The voltage output is determined by the presence or the absence of a tooth on the timing gear.

Results:

• OK - A correct signal voltage appears at the ECM connector P1 but the ECM is not reading the signal.

  Repair: Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".

  Stop.

• Not OK - The correct signal voltage does not appear at the ECM. There is a problem in the wiring between the ECM and the sensor. Proceed to Test Step 9.

Test Step 8. Check the Supply Voltage at the ECM.

1. Turn the keyswitch to the OFF position.

2. Reconnect the engine speed/timing sensor J19/P19.

3. Disconnect ECM connector J1/P1.

4. Remove wire 996-GN from the ECM connector P1-37. Install a jumper wire into the socket for P1-37.

5. Remove wire 998-BR from the ECM connector P1-9. Install a jumper wire into the socket for P1-9.

   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.

6. Turn the keyswitch to the ON position. The engine should be off.

7. Measure the voltage between wire 996-GN at ECM connector P1-37 and the digital return wire 998-BR at ECM connector P1-9.

8. Turn the keyswitch to the OFF position.

9. Reconnect all wires and connectors.

Expected Result:

The voltage is 13 ± 0.5 VDC.

Results:

• OK - The voltage is 13 ± 0.5 VDC. There is a problem in the wiring between the ECM and the sensor. Proceed to Test Step 9.

• Not OK - The voltage is not 13 ± 0.5 VDC. The voltage from the ECM is incorrect.

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

  Stop.

Test Step 9. Check for Shorts in the Wiring Harness.

1. Turn the keyswitch to the OFF position.

2. Disconnect the ECM connector J1/P1 and the engine speed/timing connector J19/P19.

3. Measure the resistance between wire 996-GN at connector J19-A and wire 998-BR at connector J19-B.

4. Measure the resistance between wire 996-GN at connector J19-A and wire 999-WH at connector J19-C.

5. Measure the resistance between wire 998-BR at connector J19-B and wire 999-WH at connector J19-C.

6. Measure the resistance of the following wires to engine ground: J19-A, J19-B and J19-C.

Expected Result:

The resistance is more than 20,000 Ohms.

Results:

• OK - The resistance is greater than 20,000 Ohms. Proceed to Test Step 10.

• Not OK - The resistance is less than 20,000 Ohms. There is a short circuit in the harness or in the connectors.

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

  Stop.

Test Step 10. Check for an Open Circuit in the Harness.

1. Use a suitable piece of wire to short wire 996-GN at connector J19-A to wire 998-BR at connector J19-B.

2. Measure the resistance from wire 996-GN at connector P1-37 and wire 998-BR at the ECM connector P1-9.

3. Use a suitable piece of wire to short wire 996-GN at connector J19-A to wire 999-WH at connector J19-C.

4. Measure the resistance between wire 996-GN at connector P1-37 and wire 999-WH at the ECM connector P1-24.

5. Remove all shorts and reconnect J1/P1 and J19/P19.

Expected Result:

The resistance is less than 5 Ohms.

Results:

• OK - The resistance is less than 5 Ohms. The wiring is okay.

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

  Stop.

• Not OK - The resistance is greater than 5 Ohms. There is an open circuit or excessive resistance in the harness or in the connectors.

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

  Stop.