3408E and 3412E Engines for Caterpillar Built Machines Caterpillar

The engine speed/timing sensors provide information to the Electronic Control Module (ECM) by generating pulse signals as the timing reference ring rotates past the sensor pickups.

The secondary engine speed/timing sensor provides continuous operation of the engine if the primary engine speed/timing sensor fails. The loss of signals from both engine speed/timing sensors will prevent the ECM from actuating the injectors. To prevent any unnecessary down time, repair any problems with the speed/timing circuit at the earliest possible convenience.

The engine speed/timing sensors receive supply voltage from the ECM that is regulated at 12.5 ± 1 VDC. The engine speed/timing sensors provide a pulsed DC output voltage with a frequency that is directly proportional to engine speed. A unique tooth on the timing reference ring generates a duty cycle in order to provide the ECM with information on the crankshaft position.

Illustration 1	g00668866
Schematic

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the keyswitch to the OFF/RESET position.

2. Thoroughly inspect ECM connector J1/P1, engine speed/timing sensor connector J20/P20, and engine speed/timing sensor connector J44/P44. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Check the harness and wiring for abrasion and for pinch points from the engine speed/timing sensors to the ECM.

Expected Result:

All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasions, and of pinch points.

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Repair the circuit. Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check for Diagnostic Codes

1. Connect the Caterpillar Electronic Technician (ET) to the data link connector.

2. Turn the keyswitch to the ON position.

3. Observe Logged Diagnostic Codes on Cat ET.

Expected Result:

Cat ET indicates one of the following diagnostic codes as being active or recently logged:

• 190-03 "Engine Speed open/short to +batt"

• 342-03 "Secondary Engine Speed open/short to +batt"

Results:

• OK - 190-03 "Engine Speed open/short to +batt" present -

  Repair: Disconnect the known good engine speed/timing sensor (secondary engine speed/timing sensor).

  Proceed to Test Step 9.

• OK - 342-03 "Secondary Engine Speed open/short to +batt" present -

  Repair: Disconnect the known good engine speed/timing sensor (primary engine speed/timing sensor).

  Proceed to Test Step 9.

• Not OK - Proceed to Test Step 3.

Test Step 3. Check the Engine Speed/Timing Sensor

1. Turn the keyswitch to the OFF/RESET position.

2. Remove the suspect engine speed/timing sensor.

3. Inspect the plastic sliphead for damage.

4. Check the tension on the sliphead by gently prying out the sliphead 3 to 4 mm (0.12 to 0.16 inch). Push in the sliphead from the extended position.

5. Extend the sliphead.

Expected Result:

Pushing in the sliphead from the extended position should take at least 22 N (5 lb) of force.

Results:

• OK - The engine speed/timing sensor and the sliphead are undamaged. The tension on the sliphead is normal. Reinstall the sensor.

  Repair: Reinstall the engine speed/timing sensor. Refer to Disassembly and Assembly, "Speed/Timing Sensor - Remove and Install".

  Proceed to Test Step 4.

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

  Repair: Replace the engine speed/timing sensor. Refer to Disassembly and Assembly, "Speed/Timing Sensor - Remove and Install".Calibrate the new sensor. Refer to Troubleshooting, "Engine Speed/Timing Sensor - Calibrate".Verify that the repair eliminates the problem.

  STOP

Test Step 4. Check the Engine Speed on Cat ET

1. Turn the keyswitch to the ON position and crank the engine.

2. Observe the engine speed on Cat ET while you crank the engine.

Expected Result:

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

Results:

• OK - The engine speed/timing sensor is operating normally at this time.

  Repair: Reconnect the known good engine speed/timing sensor.If you are troubleshooting an intermittent problem, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• No Engine Speed - The engine does not start and the engine speed does not appear on Cat ET. Proceed to Test Step 5.

• Engine Speed OK/Engine Will Not Start - The engine will not start. Engine speed appears on Cat ET.

  Repair: Reconnect the known good engine speed/timing sensor.Proceed to Troubleshooting, "Engine Cranks But Will Not Start".

  STOP

Test Step 5. Check the Supply Voltage at the Sensor Connector

1. Install a 7X-6370 Adapter Cable As (3-PIN BREAKOUT) at the suspect connector for the engine speed/timing sensor.

2. Turn the keyswitch to the ON position.

3. Measure the voltage between Terminal A (+V Timing) and Terminal B (Digital Return) of the breakout.

4. Turn the keyswitch to the OFF/RESET position.

Expected Result:

The supply voltage is 12.5 ± 1.0 VDC.

Results:

• OK - The engine speed/timing sensor is receiving correct supply voltage. Proceed to Test Step 6.

• Not OK - Proceed to Test Step 7.

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

1. Remove the wire from Terminal C (Signal) at the harness side of the suspect connector for the engine speed/timing sensor.

2. Measure the voltage between Terminal B (Digital Return) and Terminal C (Signal) of the breakout. Perform this step with the keyswitch in the ON position before you crank the engine and while you crank the engine.

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

4. Reinstall the wire in Terminal C (Signal) of the suspect connector for the engine speed/timing sensor.

Expected Result:

The voltage is less than 3.0 VDC or the voltage is greater than 10.0 VDC with the keyswitch in the ON position. The voltage varies between 2.0 VDC and 4.0 VDC during engine cranking.

Results:

• OK - The engine speed/timing sensor is producing an output signal. Proceed to Test Step 8.

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

  Repair: Replace the engine speed/timing sensor. Refer to Disassembly and Assembly, "Speed/Timing Sensor - Remove and Install".Calibrate the new sensor. Refer to Troubleshooting, "Engine Speed/Timing Sensor - Calibrate".Verify that the repair eliminates the problem.

  STOP

Test Step 7. Check the Supply Voltage at the ECM

1. Turn the keyswitch to the OFF/RESET position.

2. Install a 7X-1715 Adapter Cable (40-PIN BREAKOUT) at ECM connector J1/P1.

3. Turn the keyswitch to the ON position.

Show/hide table



Illustration 2	g00668980
J1/P1 breakout

4. Measure the voltage between P1:29 (Digital Return) and P1:32 (+V Timing) at the breakout.

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

Expected Result:

The voltage is 12.5 ± 1.0 VDC.

Results:

• OK - There is an open circuit or excessive resistance in the harness between the ECM and the sensor.

  Repair: Repair the circuit.Verify that the repair eliminates the problem.

  STOP

• Not OK -

  Repair: Ensure that the ECM is receiving the correct supply voltage. Refer to Troubleshooting, "Electrical Power Supply Circuit - Test".

  If the ECM is receiving the correct supply voltage, proceed to Test Step 8.

Test Step 8. Check for a Short Circuit in the Wiring Harness

1. Turn the keyswitch to the OFF/RESET position.

2. Disconnect ECM connector J1/P1 and the suspect connector for the engine speed/timing sensor.

3. Measure the following resistances at the suspect engine speed/timing sensor (harness side).
   • Terminal A (+V Timing) and Terminal B (Digital Return)

   • Terminal A (+V Timing) and Terminal C (Signal)

   • Terminal B (Digital Return) and Terminal C (Signal)

   • Terminal A (+V Timing) and engine ground

   • Terminal B (Digital Return) and engine ground

   • Terminal C (Signal) and engine ground

Expected Result:

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

Results:

• OK - Proceed to Test Step 9.

• Not OK - There is a short circuit in the harness or connectors.

  Repair: Repair the circuit.Verify that the repair eliminates the problem.

  STOP

Test Step 9. Check the Resistance through the Harness

Illustration 3	g00668980
ECM connector P1 (ECM side)

1. Fabricate a jumper wire with pins at both ends.

2. Use the jumper wire to short P1:32 (+V Timing) and P1:29 (Digital Return) together.

3. Measure the resistance between J20:A (+V Timing) and J20:B (Digital Return).

4. Measure the resistance between J44:A (+V Timing) and J44:B (Digital Return).

5. Use the jumper wire to short P1:32 (+V Timing) and P1:38 (Primary Speed/Timing).

6. Measure the resistance between J20:A (+V Timing) and J20:C (Primary Speed/Timing).

7. Use the jumper wire to short P1:32 (+V Timing) and P1:39 (Secondary Speed/Timing).

8. Measure the resistance between J44:A (+V Timing) and J44:C (Secondary Speed/Timing).

9. Remove the jumper wire and reconnect all of the connectors.

Expected Result:

The resistance is less than 10 Ohms when the jumper wire is installed.

Results:

• OK - The harness resistance is within acceptable limits. Proceed to Test Step 10.

• Not OK - There is an open circuit or excessive resistance in the harness or connectors.

  Repair: Repair the circuit.Verify that the repair eliminates the problem.

  STOP

Test Step 10. Check the Signal Voltage at the ECM

1. Turn the keyswitch to the ON position.

Show/hide table



Illustration 4	g00668980
J1/P1 breakout

2. Measure the signal voltage at the breakout, as follows:

   Primary Engine Speed/Timing Sensor

   Measure the voltage between P1:38 (Primary Speed/Timing) and P1:29 (Digital Return) at the breakout. Perform this step with the keyswitch in the ON position before you crank the engine and while you crank the engine.

   Secondary Engine Speed/Timing Sensor

   Measure the voltage between P1:39 (Secondary Speed/Timing) and P1:29 (Digital Return) at the breakout. Perform this step with the keyswitch in the ON position before you crank the engine and while you crank the engine.

3. Turn the keyswitch to the OFF position.

Expected Result:

The voltage is less than 3.0 VDC or the voltage is greater than 10.0 VDC with the keyswitch in the ON position. The voltage varies between 2.0 VDC and 4.0 VDC during engine cranking.

Results:

• OK - The engine speed/timing signal is reaching the ECM connector. Proceed to Test Step 11.

• Not OK - The engine speed/timing signal is not reaching the ECM.

  Repair: Recheck the harness and connectors for shorts, for opens, and for excessive resistance. Repair the circuit.Verify that the repair eliminates the problem.

  STOP

Test Step 11. Check Engine Speed on Cat ET

1. Turn the keyswitch to the ON position and crank the engine.

2. Observe the engine speed on Cat ET while you crank the engine.

Expected Result:

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

Results:

• OK - The engine speed/timing sensor is operating normally at this time.

  Repair: Reconnect the known good engine speed/timing sensor.Refer to Troubleshooting, "Electrical Connectors - Inspect" if you are troubleshooting an intermittent problem.

  STOP

• NOT OK - A valid engine speed/timing signal appears at ECM connector P1, but the ECM is not reading the signal properly.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.

  STOP