3176C Engines for Caterpillar Built Machines Caterpillar

Use this procedure to troubleshoot any suspect problems with the following sensors:

• Primary engine speed/timing sensor

• Secondary engine speed/timing sensor

This procedure covers the following diagnostic codes:

• 190-02 Loss of Engine Speed Signal

• 190-11 Engine Speed Sensor mechanical failure

• 342-02 Loss of Secondary Engine Speed signal

• 342-11 Secondary Engine Speed Sensor mechanical failure

The engine uses two engine speed/timing sensors. The secondary engine speed/timing sensor monitors the camshaft gear and the primary engine speed/timing sensor monitors the crankshaft gear. Both of the engine speed/timing sensors detect the reference for engine speed and timing from a unique pattern on the respective gear. The Electronic Control Module (ECM) counts the time between pulses that is created by the sensor as the gear rotates in order to determine rpm.

Under normal operation, the secondary engine speed/timing sensor is used to determine timing for starting purposes. The secondary engine speed/timing sensor is used to determine when the piston in the No. 1 cylinder is at the top of the compression stroke. When the timing has been established, the primary engine speed/timing sensor is then used to monitor engine speed.

When the timing has been established, the ECM triggers each injector in the correct firing order at the correct time. The actual timing and duration of each injection is based on engine rpm and on load.

If the engine is running and the signal from one sensor is lost, no change in engine performance will be noticed. If the engine is running and the signals from both sensors are lost, fuel injection will be terminated and the engine will be shut down by the ECM.

The engine will start when only one sensor signal is present. The engine will not start if the signals from both sensors are lost.

Both sensors are magnetic sensors. The two sensors are not interchangeable.

Complete all of the following tasks when you install a speed/timing sensor:

• Ensure that an O-ring is installed on the sensor. If the O-ring is damaged or missing, replace the O-ring.

• Lubricate the O-ring with oil.

• Ensure that the sensor is fully seated into the engine before tightening the bracket bolt.

• Ensure that the electrical connector is latched.

• Ensure that the harness is properly secured, and ensure that each tie-wrap is placed in the correct location.

Illustration 1	g01198125
Typical schematic

Illustration 2	g01288932
Sensors and mounting brackets (typical example)

Test Step 1. Check for Diagnostic Codes

1. Connect the Caterpillar Electronic Technician (ET) to the service tool connector.

2. Restore electrical power to the engine ECM.

3. Start the engine and run the engine until the engine is at the normal operating temperature.

   Note: If the engine will not start, monitor the engine rpm on Cat ET while the engine is being cranked. Cat ET may need to be powered from another battery while the engine is being cranked. Upon initial cranking, the status for engine speed may indicate that the engine speed signal is abnormal. This message will be replaced with an engine speed once the ECM is able to calculate a speed from the signal.

4. Wait at least 30 seconds for activation of the diagnostic codes. Look for these codes on Cat ET:
   • 190-02

   • 190-11

   • 342-02

   • 342-11

Expected Result:

One or both of the diagnostic codes that are listed above are logged or active.

Note: If the engine will not start and Cat ET displayed 0 rpm during cranking, select "No Engine rpm".

Results:

• No Engine rpm - Engine rpm is not indicated on Cat ET. Proceed to Test Step 2.

• Active or logged code - There is an active diagnostic code or a logged diagnostic code for an engine speed/timing sensor. Proceed to Test Step 3.

Test Step 2. Check the Installation of the Sensors and the Brackets

1. Remove electrical power from the engine ECM.

2. The flange of the sensor should be flush against the engine in order to ensure proper operation.

3. Inspect the bracket in order to ensure that the installation allows the flange of the sensor to be flush against the engine.

   Verify that the bracket is not bent.

   Note: The bracket cannot be replaced separately.

4. Ensure that the O-ring has been installed on the sensor, and ensure that the O-ring is free of damage.

5. If either of the following diagnostic codes is active, there may be a problem with the assembly of the camshaft gear or the crankshaft gear:
   • 190-11

   • 342-11

Expected Result:

The sensors and the bracket are properly installed.

Results:

• OK - The sensors and the bracket are properly installed. Proceed to Test Step 3.

• Not OK - The sensors and/or the bracket are not properly installed.

  Repair: Perform the following procedure in order to properly install the sensors and the bracket:

  1. Loosen the bolt that holds the sensor mounting bracket to the engine.

  2. Seat the sensor and tighten the bolt.

     If the sensor will not seat, repair the sensor or replace the sensor, as required.

     Note: The sensor must not be removed from the bracket.

  3. Ensure that the sensor is properly oriented and that the harness is secured in the proper location.

  4. Verify that the repair eliminates the problem.

  STOP

Test Step 3. Inspect the Electrical Connectors and the Wiring

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Illustration 3	g01197978
(1) Primary engine speed/timing sensor (2) Secondary engine speed/timing sensor

1. Thoroughly inspect the connectors for the engine speed/timing sensors (1) and (2). Refer to Troubleshooting, "Electrical Connectors - Inspect".

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Illustration 4	g01285313
Location of the P2 ECM connector (typical left side engine view)

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Illustration 5	g01197972
P2 terminal locations for the engine speed sensors (P2-48) Primary engine speed/timing sensor + (P2-49) Primary engine speed/timing sensor - (P2-58) Secondary engine speed/timing sensor + (P2-59) Secondary engine speed/timing sensor -

2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the engine speed/timing sensors.

3. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

4. Check the harness and the wiring for abrasion and for pinch points from each sensor back to the ECM.

Expected Result:

All of the 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 - The harness and connectors appear to be OK. Proceed to Test Step 4.

• Not OK - The connectors and/or wiring are not OK.

  Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.

  STOP

Test Step 4. Measure the Sensor Resistance at the ECM Connector

1. Disconnect the J2/P2 ECM connector.

2. Use the following procedure to measure the circuit resistance for the primary engine speed/timing sensor:

   1. Measure the resistance between P2-48 (primary engine speed/timing +) and P2-49 (primary engine speed/timing −).

      Note: Check for an intermittent problem (open or short) by moving the harness while you measure the resistance. Pull the wires that are directly behind the sensors and shake the wires that are directly behind the sensors.

      Resistance ... 75 to 230 Ohms

3. Use the following procedure to measure the circuit resistance for the secondary engine speed/timing sensor:

   1. Measure the resistance between P2-58 (secondary engine speed/timing +) and P2-59 (secondary engine speed/timing −).

      Note: Check for an intermittent problem (open or short) by moving the harness while you measure the resistance. Pull the wires that are directly behind the sensors and shake the wires that are directly behind the sensors.

      Resistance ... 600 to 1800 Ohms

Expected Result:

The resistance measurement is within the specifications.

Results:

• OK - The resistance measurement is within the specifications.

  Repair: The sensors and the harness are OK.

  1. Temporarily connect a test ECM.

  2. If the problem is resolved with the test ECM, reconnect the suspect ECM.

  3. If the problem returns with the suspect ECM, replace the ECM.

  STOP

• Not OK - The resistance is not within the acceptable range when the circuit resistance is measured through the engine harness. Proceed to Test Step 5.

Test Step 5. Measure the Sensor Resistance at the Connector for the Sensor

1. Disconnect the suspect sensor from the engine harness.

2. Thoroughly inspect the connector for the suspect engine speed/timing sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Measure the resistance between terminal 1 and terminal 2 of the sensor connector.

Expected Result:

For the primary engine speed/timing sensor, the resistance measurement is between 75 and 230 Ohms. For the secondary engine speed/timing sensor, the resistance measurement is between 600 and 1800 Ohms.

Results:

• OK - The sensor resistance is within tolerance.

  Repair: The problem is in the harness between the suspect engine speed/timing sensor and the engine ECM. Repair the wiring and/or the connector. Verify that the problem is resolved.

  STOP

• Not OK - The sensor resistance is out of specified range.

  Repair: Perform the following procedure in order to check and install the new sensor:

  1. Before installing the new sensor, measure the resistance of the new sensor.

     If the new sensor resistance is in the correct range, install the new sensor in the engine, as follows:

     1. Loosen the bolt that holds the sensor mounting bracket to the engine.

     2. Ensure that the O-ring is installed and free of damage.

     3. Seat the sensor and tighten the bolt.

        If the sensor will not seat, repair the sensor or replace the sensor, as required.

        Note: The sensor must not be removed from the bracket.

     4. Ensure that the sensor is properly oriented and that the harness is secured in the proper location.

  2. Verify that the repair eliminates the problem.

  STOP